What are the best shirt colors for wearing with light gray khaki shorts?

I’ve done some internet searches and some people are saying anything except grey, or things like yellow, but this doesn’t seem right.

I was thinking white, black, and red, but yellow doesn’t seem right, or maybe it’s just me.

Are there a few colors that generally always go with light grey shorts? Also, what color flip flops should I wear?

I’ve never worn grey shorts before.