Hi JD,
From a cosmetic standpoint, I would think that just about anything you put on a glove will affect the color somewhat. Even just plain water will make the glove look quite a bit darker- at least initially- but the color will seem to lighten as it dries. Anything that's wet will darken leather at first, but the effect usually isn't permanent.
It is kind of hard to guess at what would discolor a glove the least. All grades of leather seems to react differently when cleaned and conditioned, depending on its porosity, thickness and how the leather was treated from the factory.
My own experience has been that Lexol products seem to cause the least amount of color change or darkening compared to other treatments.
I would be curious to know why you are "not a fan" of the Lexol cleaner (orange bottle). I've never had any problems with it and wonder if you had a bad experience with it or if it didn't give you the results you were expecting.
The 50/50 mix of Murphy's Oil Soap and water I mentioned earlier is a good, safe cleaner for leather and works great on gloves that are lightly soiled. There again, just getting the glove wet will make it look a lot darker at first, but once it dries the color should be pretty close to original.
I haven't had a chance to check out one of the new Pro-Preferred glove care kits yet. Being a "two-step" process- one cleaner and one conditioner- and being advertised as not affecting the glove's color, I can't help but wonder if these two products are something similar to what Lexol already offers. Lexol has long had the separate cleaner and conditioner and one thing always touted in their advertising is that their products don't change the color of the leather.