I have see a pink one, but never red....
I also have never seen a red. The only pink one I have seen was on the cover of Martin Moe's "Marine Aquarium Handbook". I saw a large pink carpet years ago in a LFS that I thought was a gigantea, but over the years I am beginning to doubt my memory.
Blue Zoo Aquatics sells them. They are not in stock though.
Quickcord
I have absolutely seen a red gigantea in the flesh. It was about 10 years ago at a LA wholesaler. There were 2 of them actually. The floor manager wouldn't let me buy them because both of them had holes in their feet and they were VERY expensive.
I have never seen one since.
Another way to tell the two apart is haddonis usually have a thick "lip" around their mouth that is usually pinkish or orange-ish. Giganteas don't have the lip or the color.
Also what would be the reason they're not coming in anymore since Phender has seen them?