I’m sure it is more complicated than red and blue make purple, but I’m wondering about how the dun color comes about. I’ve read that it is a dilute bay gene (iirc) - but where does the dilute come from? Is it possible that a palomino + bay = dun? 
The dilute gene for dun is called dun and it is separate from cream (which is what causes palomino). Dun affects both black and red hair and it is dominant, meaning you only need one dun gene to be dun.
The traditional dun that you are used to seeing is dun on bay. Dun on chestnut is called red dun and dun on black is called grulla. Dun lightens the body, generally leaving a dark head, dark mane and tail, a dorsal stripe, and stripes on the legs as the color transitions from the dark to the lighter shade.
To make things more confusing, in Britain, they often use the term dun for buckskin ponies. So for example, if you’re thinking of a Connemara like *Gun Smoke, he is buckskin with the sooty gene added to create dramatic dark shading. Dun is not found in Connemaras.
The palomino (more properly, cream) gene on bay instead of chestnut is buckskin.
Depends on wether you are discussing a buckskin or dun - genetically they are different, but I have often heard them used interchangeably
http://www.animalgenetics.us/CCalculator1.asp
Offspring Color Probability for “Palomino x Bay”
29.17% - Buckskin
29.17% - Bay
16.67% - Palomino
16.67% - Chestnut
4.17% - Smoky Black
4.17% - Black
Here’s how you tell dun and cream apart:
Dun is an ordinary dominant - two copies of dun look the same as one copy.
Cream is incompletely dominant - two copies are very pale
Cream affects only red hair - the black hair is not affected
Dun affects both red and black hair.
Dun on chestnut turns the horse more pink than yellow and leaves dark chestnut points
Cream on chestnut turns the horse yellow and gives the horse a light mane and tail
Dun adds striping on the legs and a dorsal stripe.
A horse can be both dun and cream together.
Thanks. So for a horse to be a dun, does one of the parents have to be a dun? Sorry if that is a dumb question but I know nothing of genetics!
[QUOTE=Pocket Pony;6612449]
Thanks. So for a horse to be a dun, does one of the parents have to be a dun? Sorry if that is a dumb question but I know nothing of genetics![/QUOTE]
Yes. And dun is a factor (like gray) that can overlay on any base color. So the sire might be labeled “grulla” which is black dun and produce a yellow dun (bay) or red dun.
My horse is a dun - dorsal stripe, zebra stripes…the “buckskin-type” dun color, not a red dun. Is that just a regular dun?
[QUOTE=Pocket Pony;6612456]
My horse is a dun - dorsal stripe, zebra stripes…the “buckskin-type” dun color, not a red dun. Is that just a regular dun?[/QUOTE]
Sounds dun (not buckskin) to me.
[QUOTE=Pocket Pony;6612456]
My horse is a dun - dorsal stripe, zebra stripes…the “buckskin-type” dun color, not a red dun. Is that just a regular dun?[/QUOTE]
Yes, that is “regular” dun. Buckskin is a dilution, while dun is something completely different. Red dun is usually the dun factor expressed on a red-based color, i.e. chesnut. For example, my husband has a QH mare that is dun. She was bred to a chestnut last year, and produced a red-dun this year. For interest sake, the previous year she was bred to a blue roan and produced a bay colt.
Interesting, HHR.
So is there a color that a dun would breed with that would NOT produce another dun? Does it have to be a darker color like a bay/black to produce a “regular” dun color (vs. a red dun)?
I’m no color expert,that’s for sure! But a dun can produce non-dun offspring and I don’t think it matters what they are bred to. My understanding is that there is a 50/50 chance of having a dun baby if one parent is dun and the other is not. I believe red dun occurs when the dun gene is passed on in conjunction with a red gene. But my husband’s mare (the dun) could have easily had a plain chestnut foal this year; it just happened to get the red gene and the dun gene. Just like her plain bay foal from last year could have been dun, but didn’t get the dun gene.
I’m sure someone here with more color knowledge could better answer your question 
Hopefully they will chime in…
Chestnut with one or two copies of the dun gene: red dun
Chestnut with one copy of the cream gene: palomino
Chestnut with two copies of the cream gene: cremello
Bay with one or two copies of the dun gene: often just called dun or dun with black points. I THINK also clay bank dun but I may be wrong
Bay with one copy of the cream gene: buckskin
Bay with two copies of the cream gene: perlino
Black with one or two copies of the dun gene: grulla/grullo
Black with one copy of the cream gene: smoky black
Black with two copies of the cream gene: smoky cream
“One copy” means only one parent gave the gene to the offspring, either because the other parent didn’t have one to give, or because of the 50-50 chance of passing it if the parent has only one copy. If the parent is homozygous they have two copies and will pass one every time. “Two copies” means the foal got one copy of the gene from each parent and now has two… homozygous.
Googling any of the color names should give you lots of pictures.
[QUOTE=Pocket Pony;6612848]
Interesting, HHR.
So is there a color that a dun would breed with that would NOT produce another dun? Does it have to be a darker color like a bay/black to produce a “regular” dun color (vs. a red dun)?[/QUOTE]
Dun is dominant, meaning you need only one Dun gene to be dun. But, you also could have two. (The same is true for grey.)
Thus, a dun parent with only one copy of the dun gene can produce a non-dun baby. But, a dun parent with two copies of dun cannot. It does not matter what the base color is of the other parent (assuming the other parent isn’t dun).
UC Davis can do genetic testing if you want to know your specific genotype. http://www.vgl.ucdavis.edu/services/coatcolorhorse.php
Just to be clear - cream can affect the black pigment, such as the mane, as is often seen on buckskins where they have very blonde/white guard hairs in the mane. As well, double cream does indeed affect the black pigment - think Perlino and smoky cream
Dun affects both red and black hair.
Yes and no - depends on whether you’re taking about the body hair or the mane/tail A grulla - black with dun - does have the body hair diluted to some extend, sometimes barely visible, sometimes very obvious. But their manes/tails will still be black.
Dun on chestnut turns the horse more pink than yellow and leaves dark chestnut points
Cream on chestnut turns the horse yellow and gives the horse a light mane and tail
In the context of palomino being “yellow”, I agree, dun doesn’t do that, but “pink” isn’t quite right either. Red dun horses have a fairly distinctly yellow tinge to their coats, which is why it’s often very easy to tell they are dun without even seeing any other dun characteristics
Dun adds striping on the legs and a dorsal stripe.
The dorsal stripe, yes, very distinct and nearly always runs completely into the tail and into the mane, staying sharp while it does. But leg barring and other characteristics aren’t a necessity and aren’t always present
[QUOTE=Pocket Pony;6612848]Interesting, HHR.
So is there a color that a dun would breed with that would NOT produce another dun? Does it have to be a darker color like a bay/black to produce a “regular” dun color (vs. a red dun)?[/QUOTE]
Dun affects the color, period. But how easily you can see that depends on what else is going on. RFF Starbuck is a Perlino who is also Dun, but you really cannot see the dun on him. And of course, if the horse goes gray, at some point you won’t see the dun. Some buckskins and palominos are such that it’s difficult to see.
So no, if the dun gene is passed on, there isn’t any color it wouldn’t affect. It’s just then a matter of how well you can see it
There are lots of photos of dun Morgans on various base coats on the page below. There is also a perlino dun stallion on this page that shows how his dun markings show up very well on his perlino coat.
To get a dun you need: a black gene, an agouti (bay) gene, and a dun gene.
To get a grulla you need: a black gene and a dun gene
To get a red dun you need: no black gene and a dun gene. Agouti can be there or not because it won’t affect anything on a “red” horse.
Of course this is assuming there are no additional genes coming into play such as the cream gene, roan gene, gray gene, etc.
Now here’s my question - If you threw cream into the above mixes - what would you get? So basically I’m asking what a buckskin with the dun gene, a smokey black with a dun gene, and a palomino with a dun gene will look like…
ETA: Did a little research and looks like there is not an “official” color for these combinations. They are just dunskins, smokey duns, and dunalinos…
[QUOTE=Pocket Pony;6612456]
My horse is a dun - dorsal stripe, zebra stripes…the “buckskin-type” dun color, not a red dun. Is that just a regular dun?[/QUOTE]
Out of the same mare( red sorrel) and stud( dun w/ roan coloring) breeding I got a red dun who had the reddish gold color, dorsal stripe and leg barrings( a bit darker than body color) and same color mane /tail.
The second breeding produced what they called a red roan, but she was a dun colored roan with black dorsal stripe , masking, dorsal and leg barrings. Her mane and tail were black with dun hairs intermixed.
I bred above mare to a bay jack for a mule and have a dark tan dun mule with black dorsal, shoulder stripe, striping all down his legs, cobwebbing on his forehead and black/ dun colored mane/tail.
The nicest part was I wasn’t even trying for color on any of these breedings!
Unless I am wrong a dun will ALWAYS have a dorsal stripe.
A buckskin doesn’t have a dorsal stripe.
[QUOTE=OveroHunter;6613971]
Now here’s my question - If you threw cream into the above mixes - what would you get? So basically I’m asking what a buckskin with the dun gene, a smokey black with a dun gene, and a palomino with a dun gene will look like…[/QUOTE]
If you go to the website I posted above you can see photos of several duns that also carry the cream gene.
Vt - yes, dun can show on double dilutes but it might not. The darker the color of the DD the more likely the dun factor are to show.
Overo - dun on buckskin makes dunskin, with the dun often hiding in the cream but not always. Dun on palomino makes dunalino, and this can hide even more easily. I don’t believe there is a widespread term for dun on smoky black but I’ve heard smoky dun used, maybe smoky grulla. I don’t believe Ive heard a term for any dun on double dilute.
Candy - a buckskin (or bay or palomino or chestnut or…) can indeed have a dorsal stripe. It’s called counter shading and is usually pretty distinctly different fro a dun dorsal stripe in that it usually has fuzzy edges and often tapers off going into the mane/tail.
By the way, if you have dun and are trying to not see it expressed in the offspring, the obvious strategy is to breed to homozygous gray. 
The baby will still be dun, of course, just inobviously so.
