The Dreamcast swirl can always only be blue to me. It makes so much sense because blue = Sega and red = Nintendo.
The US/Japan swirl always appeared red to me as well, rather than orange
Anyway, I'm not marking the occasion or anything - which I now feel bad about! I didn't even realise it was the anniversary.
I only got my Dreamcast in 2008, so I've nothing really to commemorate. I can't even re-visit the classics seeing as I've been playing them to death over the last year or so

.
I will be re-visiting Shenmue again this Christmas though I'm sure.