The homebrew scene is going strong and one series of projects is Wario Land: Super Mario Land 3 getting the DX treatment from modder korxo.
The first entry in the Wario Land series has been colorised with this hack.
It doesn’t have the quality of the Mario Land color hacks, but it’s still better than the monochrome version.
It doesn’t run on a monochrome Game Boy, only on a Game Boy Color.
What is notable is that the original game did actually have a limited color palette support on the Game Boy color, but this romhack goes for the DX look from games like Link’s Awakening DX.