Unless or until we are able to choose forum "skin" preferences again, the "sandy" colored forums are the main ones we all know and love, the "blue" forums are sub-forums from the new "groups" feature.
And, it seems, there are two ways to interface with some of the user control pages, like your profile, so that they could be sandy or blue, depending on the approach (but, I believe, address the same database, so changes made under one color will also be reflected under the other)
For more weirdness, check out the
Archive link at the bottom of any (or most) page....
tee