If only one color is available, it should obviously be black. It's neutral. No one is going to not buy it because it's black. If two are available, I think the second option should be dark red. Partly because it seems to be the second most popular option, but also because it's been the color used for the renders on the home page and all the marketing material for ages.
Yeah, I'll have to go with this^
I'm no fan of black in general, but the color in the renders would be my choice if I had to go with an alternative that could be a second choice that would probably please the most people.
The "yellow" render was and is still my favorite, but's it's unlikely that one will see the light of day, and considering there wasn't even a sample of that color I'm not holding my breath.
Chris