Copag color loss and transfer is the #1 reason I initially started looking for suitable replacement plastic cards, years ago. Never went back.
Among several others, I tried Kem (fail - warping issues, expensive), Modiano (fail - too stiff), Gemaco Star (fail - too slick, warping issues), Piatnik (excellent, hard-to-find), Gemaco Superflex (excellent, expensive), Bicycle Prestige (excellent, affordable), Desjgn (excellent, reasonably priced), and Fournier (excellent, hard-to-find).
I have a lot of other brands and types (some decent, others not-so-decent), but my current go-to set-ups are Prestige and Desjgn, both in bridge size with jumbo index.