Yours do look a little dirtier than the snow pics you posted a while back. But if you look at your buddy's sidewalls in the first pic, they look spitshine black! Maybe it's that my tires go through more dirt while you ride lots of rocks?

Do you clean your tires? I don't. The rims every so often, the frame is kept somewhat clean but the drivetrain is cleaned and lubed after every ride (runs better and quiet that way)................By the way, I noticed that you have the same exact red tire on one of your bikes, it too is real shiny red! (Panaracer Fire XC Pro)