When I put a potion doesn't matter which, in my inventory my hearts/food turn a bit purple, see the pictures. When I remove the potion from my inventory it is normal again. (I'm not sure but I think it happened after I drink a potion of swiftness extended 8 min one.)

Edit: my cursor also turns purple, and green on quarts blocks, pillars etc.

Just found out: When you hold a melon it will remove the bug.