Millie Dubois wrote this fantastic article called There’s Always Another Rainbow: A Look at Rainbows in 80’s Cartoons. Here’s a couple of short excerpts; head over to read the whole thing!
“Why are rainbows so commonly used in 80’s cartoons? One reason could be in the rise of color TVs.”
“Another thing I noticed while watching these cartoons is how creatively rainbows are used. In animation, rainbows are very versatile. They have no fixed shape, you can show rainbows as an arch, a beam, a ribbon, a waterfall, etc. and still have them be recognizable.”