Yes, you must use low impedance charger. Luckily most chargers ARE low impedance. The point is to keep the charge through distance and some interference (weeds). More info: http://www.hallman.ca/impedance.htm Seriously, spend the money to get a strong, good charger. You won’t regret it.
Per the blog, I have the brown and green. http://2.bp.blogspot.com/-g3pyRZ40R6g/U-uR0sED1PI/AAAAAAAAA4Q/gvEkOuME_cw/s1600/20140619_085232.jpg From a distance you can’t see the variation. The nice thing about the two color is with the tape gate–it’s pretty obvious to anyone helping me out when I’m gone that the colors aren’t matching up. However, if the solid brown had existed at the time I bought the first rail, I’m sure I would have just done that. Having had a tape gate, if I were doing it over, I would just use a heavy gauge metal gate. The connectors/handles are expensive. It’s really not THAT much cheaper.
The dark color is more visible in winter the light better in summer. Dark fencing in general is more forgiving for small farms (doesn’t look as chopped up) and if you don’t set your heights perfect. Just my opinion. White is very sharp, but you better be straight! I think the horses see all the colors fine, personally. I thought black posts would be lower maintenance than white. I have seen white on unstained posts and that looked pretty nice too.