From The Wajas Wiki

Antennae are a type of Potion Mutation. They can be permanently added to your waja by using a Arista Potion. Antennae give your wajas long, insect-like antennae coming from their forehead. When adding this mutation to your waja using a potion, you may choose their color.

Mutation Appearance

All examples feature wajas with FF0000 (pure red) Antennae. However, this mutation can come in any Hex Color as well as any Texture.