I remember reading/researching/wondering about this subject quite a bit when the Color-c-lector first hit the market. I was working in a fishing tackle store at the time and a regional tackle rep loaned me a Combo-c-lector. I didn't return it for several months. I remember the tackle rep was probably more enthused about the ph function of the unit. I remember that it was very easy for the ph calibration to go "off" and it was a genuine pain to recalibrate the unit. When I say off, I mean that you could stick the probe in a glass of orange juice and you'd get a ph reading of 7. It quickly became more trouble than it was worth. I still think that Loren Hills work about ph-clines compared to thermoclines was/is valid.
I think that all things being equal, bass will seek out the most comfortable ph level available. All things aren't always equal. I'd like to have a sturdy, hard to screw up, ph meter, where I could check ph levels at different depths from time to time. For me to use it, it would have to be as easy to use as a secchi disc.
Now, about the color part of the color-c-lector. Basically, it is just a waterproof light meter. Loren Hill never could prove what colors fish would bite the best. He could only prove what colors fish could see the best. Not the same thing.
As a practical matter, using the color-c-lector was a pain. You could drop the probe into 6'deep weeds, at 9 am, on a sunny day and get one color. Half an hour later, cloudier skies, drop the probe in the same place and get a different color. Move to the edge of the weed line, get a different color. Move 50 feet down the same weed line and get a different color. Limestone bottoms read different from sand bottoms which read different from clay or gravel bottoms. Time of day made a difference. Water clarity made a difference. Every single ambient light variable that you could think of made a difference, sometimes significant, sometimes not. It wasn't always predictable. Meanwhile, day in and day out, my two best baits were a black/brown split tail eel and a green/white spotted pork frog. The color-c-lector very seldom told me to use black & brown or green & white. All of my combo-c-lector experiences took place in Central Missouri, on strip pits, small to medium sized ponds and small to medium sized conservation lakes in and around Columbia, MO.
I can't say my experiences would be duplicated elsewhere around the country, but I can't say that they wouldn't be either. I think that as a practical matter, you are better off using other methods to choose what color. Close your eyes, reach into your worm bag and pick one would be just as reliable. I've still got my combo-c-lector but it has been several years since it has gotten wet.
I think all of that 80's color/ph research was interesting, but for everyday fishing, the info needs a better delivery system to make it worth your time.
Oh, sorry, I digressed and didn't answer the question. The reason I limit myself somewhat in color selection is because it is just easier. Just pick a color, based primarily on prior experiences and go with it. If that don't work, then pick another one. Me, I've got to throw a color for at least half an hour before I'm convinced that it isn't working. Also, I think that the reason any particular color doesn't work is because I didn't put it close enough in front of a fish. So basically, my answer is "I dunno. . . ."