I think they are great for staple colors. (Been wanting a black with GHW one and a light pink with GHW one.) Some people do make the really crazy prints and colors work, but for my lifestyle, I prefer the solid colors. I prefer fine jewelry if I'm going to wear jewelry that day, so in order to get more wear out of it, I would probably choose neutral colors for myself. (I think they're wonderful, and would love to be getting 3 or 4 of them, but don't think I would build up an entire costume jewelry collection, for my current needs and lifestyle.)
But this is only my opinion for my own lifestyle and current needs. I have seen other people rock these Hermes Clic Clacs in bolder colors and crazy prints, this one girl I know even makes it a whole look (plans her daily outfit around her Clic Clacs.), and I think it looks marvelous on them.
Another thing to consider, is the price increases. I have no idea how it works with Hermes, only how it works with Chanel. But if a Hermes Clic Clac is something you have been wanting or pondering about for years, then absolutely get it before the price sky rockets. You'd have to check facts on when their increases are, and if it affects Hermes costume jewelry.