Plugged my Pi into our old TV for the first time yesterday, using composite, it worked ok for a while, then flickered into black/white.
Fiddling round with the cables, I discovered that just holding the Pi in my fingers was enough to get it to display in colour again. I think (my fingers are too fat to be sure) that just 'shorting' the whatever-it-is labelled
C74 seems to do the trick.
Any ideas what this could be? Or should I be hacking
config.txt to force into a different mode?