Mega Rainbow” = the Dilophosaurus has two special modifiers:

• Mega: likely refers to a higher weight / larger-size variant (bigger than “Huge”, “Titanic” etc.). Usually means more strength in pet effects (cooldown reductions / XP boost), since many pet skills scale with size or weight.

• Rainbow (from hatch): this mutation gives a cosmetic + bonus effect to the pet’s passive trait (often boosting stats like XP or cooldown advancement). Hatch Rainbow means it came with that mutation right when it was born, not mutated later