I am alway leary of these sort of saddles. If the tree isn't well made and it doesn't fit your horse, then the color doens't matter. YOu'll have a sore horse and a pretty saddle.
If it's just a matter of the color, it is kind of cool but may be harder to make out with a pattern on a patterned horse. I would use a solid color to emphasize the pattern of your horse. And, yeah, a pink blanket would look cool.