A Ph.D. in "colorology" (I made that one up) shouldn't be a prerequisite for picking the right bait. While the number of color options are dizzying, there's a few fish fundamentals that form the foundation for choosing the right one.
In reality, few fishermen need a sack full of color combinations to consistently bag fish. Admittedly, there are times when that fire tiger with purple polka dot paint job slays 'em like nobody's business, however, those are rare times at best.
Rest assured, when settling on a color, a very general set of rules apply to the majority of conditions. If you take nothing away from this, remember: color selection is primarily predicated by its ability to visually stand out under varying weather and water conditions.
Here are some general guidelines for selecting the right color to match the situation:
1. Clear Water. Color selection is critical when faced with clear conditions as fish are able to give baits a serious once-over from a distance. In clear water—match the hatch. I hate using that all-so-tired cliché, but it's so applicable. Clear water dictates a pattern that closely mimics the predominant baitfish in the particular bay, bayou, river, flat or blue water you're fishing. If it's killifish, then by all means use a killifish pattern. Knowledge of the local water always helps with clear-water color selections.
2. Semi-Stained Water. In mildly stained water, opt for relatively neutral colors. Why this may be hard to believe, in the water, blue, red and orange all appear neutral.
3. Overcast, Dark Days. When overcast, opt for dark colors; these include black, gold and varying shades of gray.
4. Bright, Clear Days. On bright, bluebird days lean toward light colors. These include white, chartreuse, chrome and silver.