In some cases you can I don’t think anyone would confuse this for flaxen liver
http://i53.tinypic.com/20jpr1h.jpg
Or this for SD
http://travmuseet.com/uploads/images/webbalbum/N/Nu-Pagadi.jpg
But I agree, there are a lot of presentations that could be one or the other, though even then, usually (not always!) you can look at the color the hair around the pasterns and determine red-based vs black-based.