Diversify Cave Lighting with Colored Crystals

As of right now, caves are only lit with glow lichen. Lichen provides a good general light source for all types of caves, but caves would feel a lot more unique if more light sources were added.

Luminescent crystals of different colors would really liven up caves. Crystals could function like candles and sea pickles, increasing in brightness as more are added to a block, and they could be scattered throughout caves or only found in their own cave types, growing on the floor, walls, and ceiling.

Crystals could even be renewable: when dripped on (or maybe in/by water), a crystal would spread very slowly, adding another crystal to its own block or an adjacent block. Over time, this would result in beautiful crystal patches in wet areas.

Crystals could be purely decorative/lighting, but crystals also open the door to powdered crystal in the future, which could be used to craft other glowing blocks.