Why are Pink 1 or 2 tinted eyeglass lenses covered by insurance?

This is a rather obscure question. I was reading through the details for my vision plan at work, and in the list of items that are not covered, it says “photochromic or tinted lenses other than Pink 1 or 2”.

Anyone know why there are the exceptions for pink tint? I presume it’s a medical thing rather than a cosmetic thing, but haven’t been able to find anything relevant on Google.

Pretty much a SWAG here, but people with severe color blindness sometimes wear one tinted lens and one normal lens. The tint causes enough of a shift in the color “seen” by one eye to let them distinguish colors they normally could not.

I always thought it was a red lens but I suppose pink counts as red.

These tinted lenses (one of which appears pinkish) are used for treating depression.