I think I'd go with greys and blacks. I don't really care about sidewall color.
Green was cheaper a while ago so I put them on my Colnago. I kind of liked them as it gave the bike a little extra color, but at least people on the RBR forum thought they clashed
They're getting pretty bald now, so I'll have to decide what to put on for next summer.
Yellow would pick up some of the color of logos, but I fear it would pick up too much road dirt.
I'm not quite sure what is next. I have a pair of Gatorskins and a pair of gator hardshells that I'll probably use which will give a dark brown sidewall.
But,. I choose the tire more based on the tire characteristics I want rather than the colors.
Or, perhaps I'll put the bald green Elimin8ers back on, and for the most part use other bikes.