I was thinking that it would be nice if fans had their choice of choosing which colors to view this forum. I still prefer the older colors to the colors that are currently used. Just my two cents for what it is worth. ;)
I think most of the reason there's only one is that since it's embedded into the site, it looks better if it matches the rest of the pages.
I liked the blue too though. XD
This was asked before (actually, it's asked every time we update the site :P) but like Kelsey said, it would not match with the rest of the site. Since the site only has one design, the forum will only have one theme.