There are 2 bands with the name Blues.

A.) BLUES, formerly known as Blues For The Martyrs, is a progressive hardcore band from Tucson, Arizona. They currently have one 5 song EP available called "Death and Taxes", and a full-length called "Snakepit" with a new release forthcoming in Fall 2008 called "Heavy Sci-Fi".

B.) Blues is a Swedish rapper that emerged as one of the first big names in the upswing in popularity that the swedish hip-hop scene experienced during the late 90's.

His first and most popular hit single featured a sample of the eponymous song "Under ytan" by Uno Svenningsson, which was already before widely considered a classic by many swedes. Many found this move to be higly original as Swedish rap often was, and still is, highly focused on American styles and samples. Others accused Blues of riding on the success of the original songwriter.
Whether this was true or false, his first album "Samhällstjänst", released in spring 1999, was never a great commercial success. Possible cause of this lack of success might have been lack of exposure from the label possibly combined with the effect of Blues' low key attitude.
Probably the great simultaneous success of fellow Swedish rappers Ken Ring and Petter added to this effect. As Petter appealed largely to ethnical Swedes, Blues and Ken were perceived as spokespeople of the growing group of first and second generation immigrants. As such, the much controversial Ken was often much more interesting than the pensive and laid back Blues.

Blues released two more albums, "Ny tid, ny strid" (2001) and "Den där Blues" (2002), both with even lesser success than his first.