The coloration of this Rathalos is produced because of a mutated poison gland, the mutation causes the gland to fuse with other organs and consume color pigments, replacing them with poison drops, this mutation happens before the Rathalos hatches from its egg, a small percentage of them die due to not being able to stand the poison, surviving ones are usually the childs of a powerful Rathalos. It should be noted that G-Rank ones have a darker tone, due to the poison being stronger, but both versions will become pink for some time after using movements that require major quantities of poison.