The more I think about this the more sure I become of it.
There seems to be an ever-increasing number of colored or painted coins coming out of certain countries the last few years. At first I thought they were potentially neat but the more I've thought about it the more I've grown to dislike the basic concept.
One of the things that always made me love coins (especially silver ones) is that they are metal and they are SHINY. Plastics and other materials will never hold the same sense of strength and awe that metals do. Putting paint on it just ruins this IMO. It just doesn't feel like a coin anymore once you do that. Yes, the colors can help the details and the design "pop" more, but a good design shouldn't need it. I also tend to resent the colorized coins because they seem to have opened the door to other things that I find simply gimmicky, like putting gem-stones into the "coin." When you do that it's not a coin anymore, it's a gem mount. These things do not deserve to be called coins, they are simply novelty items.
This tends to get really disappointing too because there are some coin designs that I love and would like to own, but they only come in colorized versions. The idea of buying that makes me cringe. I'm left torn between wanting the coin for the design, the symbolism and the history, and not wanting to have painted coins in my sets.
I think it's worth drawing a distinction between the colorized coins (which have non-metallic materials added to the surface) and the Canadian hologram coins. The Canadian holograms use micro-scale manipulation of the coin's surface to change the refractive-index of the metal. The surface of the coin is still metallic however. This doesn't bother me. (Actually, as a chemical engineering major I find it fascinating from the viewpoint of materials science.) I only object to things that challenge the concept that a coin should be made of metal; no ifs. ands, or buts.
As certain countries like Australia increasingly issue colorized coins, I may find myself increasingly locked out of the market for certain fun issues because of this self-imposed prohibition. I may ultimately fold and buy a couple of these things, but for now, I really don't want to.