A couple if years ago, my husband and I were laying in the backyard looking up at the sky. Clear, sunny day and we were just relaxing. Very high. I saw this kind of iridescent dot. Hard to tell the shape because it was so high, but the color change you described reminded if it. Like when you see rainbow sheens in a puddle. It was moving at a pretty fast pace and not like a plane. I asked my husband if he saw it and after a pause he said he did. It didn't go away, but just kept moving within the general vicinity. We watched it for several minutes. Weird. I think my husband found a couple of videos online afterwards that had the same thing.