Function over form is always the priority, I was referring to the same weapon in two different styles. Thank you to mmcbeat for the tip on holster wear... Something to think about.
As far as sunlight, in my opinion the glossiness of the firearm will make more difference than the color. IE, that S&W's high gloss blue WILL reflect sunlight more than the stainless Kimber.
However, I see your point as far as cover / under garments. If you are wearing a white tshirt under your gun, a stainless / silver gun should be less noticeable than a black gun, where if you were wearing a black, or dark, undershirt, then the black gun may be preferable to the silver gun.
Again though, my opinion worrying if the gun shows against the undergarment when exposed is such a small factor I don't even think about it daily when getting dressed. I would much rather spend the time thinking about whether my cover garment is adequate to conceal my gun rather than the color of the gun standing out.