It's just how the palette is for this specific level. I think it is supposed to mean you are coated in honey or some sort of sap? It attracts flies, if I remember correctly.

If you look at the Youtube gameplay I linked earlier, level 3 starts with that pink color. I'm going to attach some screens from level 3 and even from previous levels and there's nothing like that. That's why I'm surprised.
I've also reached the final gorilla boss, which is seen in the Mobygames screenshots, and it's not pink. In my screenshot it's at night, I didn't get the item that makes the sun come back, but I assure you that the gorilla wasn't pink.

Solved! The problem was seeing it in Mobygames like that, and in that gameplay on Youtube, which only affects level 3... and I thought there would be support for EGA in that game, although I hadn't heard of it.

It turns out that from what I've read on another forum, it's the result of a cracked version by Hybrid, which gave problems, among other cracked versions that gave different problems when playing Prehistorik 2.

So solved, in case anyone was wondering too. Thanks and sorry!