/u/fairlanes:

On a re-watch of the newest episode, “Message Received”, I noticed that when not viewed through the yellow filter of the “screen,” Yellow Pearl’s colors aren’t monochromatic yellow. So, I did a few adjustments.

…which then leads me to wonder if Blue Diamond’s pearl is actually monochromatic blue, and if Pearls just have a color palette than implies the iridescence of the nacre in actual pearls – iridescence being technically “a lustrous rainbow-like play of color caused by differential refraction of light waves”. And all pearls, even colored ones, are iridescent and display subtle hints of the full spectrum of color.

So a) all Pearls may have a more varied palette; b) this causes Pearl and Rose forming Rainbow Quartz (the rainbow quality); and c) Pearl and Amethyst forming Opal (a very iridescent gem) make even more sense than they already did.