I think you're seeing a moire' effect of the pink dots screened on the inlay and the pebbled surface of the plastic overlay. Not all the chips show it; it depends on the random alignment of the printing the the surface pattern from the mold.
We discussed a similar effect a few days ago on this board on the Caesars Tahoe dollar chip. There, the pattern covers the entire center inlay and can result in one of several different 'interference' patters.

DonL