Some of the earliest $2.50's were from Reno and Lake Tahoe and were many colors, including grey, lavender, green, yellow, and brown.

Later Nevada standards on color (such as they were) did call for a pink $2.50, but many casinos in Southern Nevada chose other colors like blue and even orange. It's true, later Las Vegas snappers were mainly pink.

I don't think the name came from the color.

The Hard Rock "Pink Taco", made at the time of the 2002 Club Convention and offered to members who had a free coupon may have been the pink chip you are thinking of. It had no denomination, though.