I think that having your lure in the right spot and right depth is most important, followed by the speed and action.
On some lakes it seems like one color works particularly well. Sometimes particularly well for one boat, and a different color works for another boat. One year in Canada, some newcomers stayed at the same resort as my dad and I and they thought the color was bright orange. Everything they used was, or had some, bright orange on it. But for all of the years we had spent there we thought that the color was white. And if you ask the camp owner he'd say that purple is the color you should use.
My dad and a Northern Wisconsin guide both, independently, came to the conclusion a few years ago that their favorite Rizzo Whiz was one with a chartreuse blade and an orange body with yellow tentacles.
The muskie trollers on Lake St. Clair seem to think that the color of the lures' belly is most important, yellow or white.
I recently read an article about bass fishing with soft plastics. The author used brown and green lures exclusively. I have not used browns and greens too much because I figured that if I am unsure of the color then I should use the color I am most comfortable with, white. But I plan to try more browns and greens in the future.
I think that there are
1. Most colors are designed to catch fishermen not fish
2. Rapala, one of the most popular lure manufactures, sells the most silver and gold lures for a reason. I'll bet that there is no body of water in the world that does not have small gold or silver fish in it
3. If you think a particular lake likes a particular color, then you will have more confidence fishing there because you think you have something figured out about that lake. The more confidence you have in a lure the more you will use it and, subsequently, the more fish you will catch on it.
I think that if you are buying fishing lures you should first find lures that work well, not focus on the color. I am most confident with white lures because I think that they will be easy for fish to see and are more of a natural color.
Sometimes unnatural colors work well for muskies, but if you are unsure buy lures that are naturally colored.
Lets leave the focus on color to the walleye fishermen.