You beat me to it
Double dilutes can also have a greenish hue to the eyes as well:
The way I see it, a "white" horse is white because of one of 3 effects:
- Graying. These horses are born any other base color, and gray out over time, eventually becoming solid white. Their skin remains the same color it was, though- gray under colored areas, and pink under any white markings that were there at birth.
- Pinto patterns. Maximum sabino, dominant white, etc. are examples of pinto horses that essentially covered in one giant white spot. The hair is completely white, and the skin underneath is an unpigmented pink. They may have dark eyes, or they might have vibrant blue eyes (the frame and splash pinto patterns will sometimes produce blue eyes like this)
- Double dilutes/psueo double dilutes. Horses with two cream genes are considered double dilutes- the base color has been affected with a "double dose" of dilution producing anything from white to a very pale shade of the base coat. The skin is pink, but is still lightly pigmented. Horses with a cream gene + another dilution gene (like champagne or pearl) can have a very similar appearance to double cream dilutes and are often called pseudo double dilutes.
Oh, and there are some appaloosas that are essentially completely white, too. But appaloosa still confuses me