I’m a little late to the discussion but here’s my take:
KH blue: Not my favorite, but for historical reasons. Before there was KH, Tommy Miller made the cool, custom unicycles. And he painted them all blue, a very similar shade to the KH’s that came later. Apparently this was his “default” color, as he had either purchased a very large quantity of it or because it was the least costly of the Schwinn colors he had access to. You could order custom colors, but this would slow down delivery and raise up the price.
So when KH started using almost the same blue, I was disappointed. But if you only plan to use one color, blue is one of the better choices, based on market of market research for various products. It’s going to be perceived positively for a large majority of people. To offer multiple colors instantly ups your costs in inventory, and also increases the chance that you won’t be able to fill orders because you will have run out of a color the customer wants.
I like red but as a “standard” color, it’s not for everyone, and is likely to turn off more customers than blue. I also want my unicycles to stand out from the crowd, which would be a (small) problem if there were lots of other red ones. I would still buy red if it were offered though. Before I got my KH Muni in 2016, I had a red Wilder. I had to wait a long time for it, because I wanted red. So I got it in 2003 instead of 2002. Always loved it, in part because it might have been the only red one, and also because of what a cool uni it was.
Black? Boring. The upside is that it’s a neutral color; any other color will go with it. The downside is that it doesn’t stand out at all. But lots of people seem to like black also. Motorcycle riders tend to like a lot of black, at least on Harleys. I would be less inclined to buy a black one, though if it’s a KH and that’s the only color, I would still know it’s top of the line.
Mad 4 One offers a delightful range of colors, which I like. You pay more for having that choice, but people who like the colors have definitely been buying and enjoying them as well.