Phototransistors for the visible spectrum will be messed up by daylight unless you put something around it to block out the light. IR sensors can be messed up a little by daylight, though they are not as prone. If you were to modulate an IR signal to be reflected from the surface that would eliminate most any interference.
It's hard to say exactly what reflects IR and what doesn't, it's often about the same as the visible spectrum, ie white objects reflect it and black absorbs it, but you can set up a test circuit with an IR led and sensor to see how much it actually reflects.