An expression that indicates that one thing evokes thoughts of another.

It says here in the paper that today, the FBI announced that in an attempt to track potential terrorists, all individuals from the Middle East or who had attended universities where more than 5% of the students came from the Middle East would be required to wear yellow armbands in public. Shades of the Third Reich!

I don't know the origin of this expression, but it appears to derive either from "shading," suggesting that the first thing is like the second to some degree, or from "shade," in the sense of spirit or ghost: the first thing is being reincarnated in or possessed by the second.