I believe the two I colored took 1-2 hours each. One reason- lots of layering! Every recolor I do will also have freehand painting done on the mane and as further detailing around the face. A silver black I tried out a while ago took maybe 20 minutes, without detailing, as he only had two shades of black and a white diamond. Will have to make one of my more colorful horses in this grayscale to see how long that takes. I imagine the more white the horse has the quicker it would take as well.