how to get rid of buildup in hair without striping color?

I recently dyed my hair red and now I have a lot of gunk built up around my scalp. It's absolutely disgusting and greasy. I had this problem when my hair was permed a year ago and hoped it was just some allergic reaction to the chemicals, because it went away eventually, but now I'm having the same problem again! I want to maintain the red hair color, but I want to get this nasty residue out of my hair. So, how can I get rid of it, and what should I do to avoid it happening again?