Besides 'In the Dark' has Oz ever actually seen Spike?

And, how many different colors did Oz have his hair?  Thanks!

I don't think so... those two always seem to just miss each other. As for Oz's hair, it's at least 3 different colors - it's naturally red, but he dyes it black and blond. There might possibly have been a shade of brown in there, but it could've just been the lighting.

It's been a few shades of red, plus black, platinum blonde, and blue. The blue was only in one ep, I'm pretty sure. The red varied from strawberry blond to more intense red, any time he went back to a natural hair color. His natural color seems to be the orange-y red.

Seth did 39 episodes of BTVS, credited for 40 on IMDB.  The black hair lasted long enough to film a few movies.
Here's a site to go through BTVS Oz pics: http://seth-green.fan-sites.org/gallery/index.php?cat=8