Might sound kind of odd, but I want to take a friesian or any black/dark horse and make it white.

I would desaturate the horse (after doing all the basic prep like cutting and smudging), up the brightness and contrast to how you like it, and then use color balance and/or hue/saturation to make it off-white enough to fit the background, but here are some tutorials.

Thunder River said:
I would desaturate the horse (after doing all the basic prep like cutting and smudging), up the brightness and contrast to how you like it, and then use color balance and/or hue/saturation to make it off-white enough to fit the background, but here are some tutorials.

http://aquiloniuslupus.deviantart.com/art/Horse-Color-Black-To-White-378103755

http://joleisha.deviantart.com/art/Horse-Colour-Tutorial-270316353

Thank you so much! Those tutorials were both very helpful, and I'll take your advice as well.

No problem :) glad to help!