Pulled deli ham from the fridge and noticed a rainbow-like shine on the slices. Is that normal?

light diffraction is maximized, resulting in the characteristic rainbow sheen.
Furthermore, the use of sharp, precise slicing tools ensures a clean cut, which can also contribute to the appearance of iridescence. The smoother the surface of the slice, the more likely it is to reflect light in a way that creates the shimmering effect.

Certain additives and curing processes can influence the degree of iridescence observed in  deli ham. For example, phosphates are often added to enhance the ham’s moisture retention