From community member FakeShemp
When dealing with reflective media, such as CDs or covers with foil prints, flatbed scanners struggle a bit. CDs usually end up with rainbow patterns and hot foil prints can end up solid black. To counteract these imperfections, a layer of diffusion media can be added between the scanner glass and the medium you want to scan.
A diffusion media is a semi-transparent sheet that scatters the light passing through it (diffuses it) and makes reflections and rainbows “wash out” from the scanned image.
Without diffusion paper
With diffusion paper
There are several materials that can achieve this effect. There are even professional diffusion gel sheets you can buy from photography stores, but other materials may work as well.
If you’re using a color swatch to create a color profile for your scanner, you may create a separate one for diffused scans. Just scan with a diffuser between the scanner glass and the color swatch. Then create a new color profile like usual, but from the diffused swatch scan. This profile will make the colors more natural, even with the diffusion, but remember that the results will not be perfect, as the diffuser will mess with the light passing through it. I recommend scanning reflective media both with and without a diffuser, and using both scans as sources when cleaning the scans later on.