No, you can set any CSS color if you have the minimum karma required. The linked page is just a list of colors that users have actually set.
I really wish any user could set a custom topcolor. I found the default orange hard on my eyes, and I was glad when I could change it.
Mine is #d0c8b5, which is simply a darker version of the page background color. Plain and unobtrusive, and the bit of orange in the "Y" logo sits nicely in the corner.
And you can always use user.css to adjust per site CSS to your preference. I use it for a few sites; there are addons that facilitate it, but I've never bothered.
I really wish any user could set a custom topcolor. I found the default orange hard on my eyes, and I was glad when I could change it.
Mine is #d0c8b5, which is simply a darker version of the page background color. Plain and unobtrusive, and the bit of orange in the "Y" logo sits nicely in the corner.