It really depends on the aggressiveness of the fish. Most Crankbait's are "moving" and the fish only have a few seconds to react, (or not). As a rule I like to use red, gold, or silver eyes- with an emphasis on red! Why red?? Have you ever heard the expression,"He saw red!". Red eyes can bolster a fish's reaction strike by making them (for lack of a better word) "mad". When do colored eyes NOT work as well or make as big of an impact?
My Answer is: When the clarity of the water is extreme (clarity of 15 FT plus) and in conjunction, when using a suspending Crank, (where you are letting it pause right in front of the fish's nose). It is my belief that you'd want a more realistic looking Crank as the clarity of the water gets better and COLDER. (Cold water typically allows fish to SEE better-for a variety of reasons.) SO, silver eyes would probably be a safe bet in super-clear water. However, in fishing, all "rules of the road" are not set in stone. Some days they want a bright purple/red lure with pink highlights and GREEN eyes! (Go figure!) We can only make our best guess and go with that!
What do you think????