For example, when I trained my Nidoking, it had gold EVs when I checked it. For Lopunny, (it was a Buneary when I trained it) it was blue. If you don't know what I'm talking about, go to the summary page and press Y.
Do you mean the EV graph? When a Pokemon hasn't gained max EVs yet, it's gold. When a Pokemon can no longer gain EVs, it is blue.