I opened my right eye when I woke up from REM sleep. Over the next few moments, I had both a narrowish red streak and a larger yellow splotch briefly overlay my vision before settling on clear white light. Is that the eye adjusting to sunlight, the nervous system coming out of REM, maybe something my left eye was "seeing" that got overlaid? Odd.
Maybe I was "dreaming" it. I came fully out of REM, and it was gone.