Note: this was originally posted on page 15 of a thread in Comics General on August 31st. We're creating it as an announcement to make it easier to find.
The “rainbow effect” or “Newton rings” are a normal occurrence when two different plastics (which have different refractive indexes) are placed together. It’s what you sometimes see on a smartphone screen protector or on the edges of an LCD screen.
The rainbow effect has been seen in CGC holders since our first-generation holder was