Blocks & Decoration "Common" or naturally spawning things (not ores) can generate Dyed and/or Painted, matching biome.

[S'AraisVanu]

Just a weird QoL thing which would add variety. Blue dirt, red mud, gold that's reflective gold. you name it. Acid Blue mushroom biome for maximum trippy.

For a primitive example, check out this, however the mod's limited depiction can make some items and ores hard to see; and you don't have control over what's what. Still, a White Jungle is pretty neat, and Glowing Mushroom copys whatever it's dyed; meaning Mushroom Moss will be yellow, as will the giant mushrooms. Everything else, like the light, remains blue.
https://forums.terraria.org/index.php?threads/painted-hills-tie-dye-your-worlds.60817/

 

[Baconfry]

Why would a naturally generated world have blue dirt in it?

 

[Jetstreme ∞]

It’s interesting as a concept, but I think it’s better suited as a mod. It would be a bit confusing

Why would a naturally generated world have blue dirt in it?

Because it’s about a little guy that lives in a blue world, and all day and all night and everything he sees is just blue, like him, inside and outside

 

[S'AraisVanu]

You lunatic.
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Why would a naturally generated world have blue dirt in it?

Same reason a naturally generated would would have red sand in it

 

[Baconfry]

I can kind of see where you’re going with this. Mushroom biomes were already trippy to begin with, so I absolutely agree that introducing even more color to mushroom biomes would enhance the trippiness. Not even necessarily through paint, but just natural color variation like we see in moss.

However, I think it would probably be best to confine the trippiness to the part of the game that was intended to be especially trippy. Any further than that, and we’d be entering territory that (as Jetstream said) would be better suited to a mod (which already exists).

 

[Sigma90]

This would be a nice way to add some variety, but only at points where it would make sense. Blue mud for mushrooms could work, as might purple dirt/stone for Corruption. Or a red/orange sandy desert.
My only concern (for lack of a better phrase) is that you would need to remove the blocks, and the background walls, and the paint if you wanted to landscape an area. Some people may object to the addition of a third step.