[Al Skierkiewicz]

You guys know that due to the nature of the retro reflective tape, only light coming from your robot or directly in front of or behind your robot or the target is actually reflected back to your camera? The reason green LEDs work so well is human vision is more sensitive in the green spectrum so the camera is more sensitive in that area to mimick human vision.
If you are receiving a white image of the target, it is possible you are receiving so much light from the tape that the camera is actually white clipping the video. White clip prevents output video from exceeding a certain value and so additional light causes all three colors to "clip" off the top and return a monochrome signal above that level. The result is a zero chroma signal during that interval.