Rainbow Crystal Cave

Mushroom Fields are the rarest non-variant biomes in the biome, but why not implement the most rare cave in the cave?
As the name suggests, the rainbow crystal cave is a cave with rainbow crystals, and the rainbow crystals are the ore produced in the cave and also serve as a light source.
Only certain mobs will spawn in this cave.
That particular mob ... it's a bug-shaped mob called a "rainbow bug".
Only this mob will spawn.
If you have any other good ideas, let us know in the comments.
Thank you for taking a look at my thoughts.