ModsJava
MCRGB - A Colour Picker for Blocks
Search for blocks based on the dominant colours in their textures.
I don't know my version or loader
Open the Minecraft launcher and look at the profile you play on — it names both, like fabric-loader-1.21.4. The version also shows in the bottom-right corner of the game's main menu.
No loader in the profile name? Then it's plain Minecraft, and these mods won't run — you need Fabric or NeoForge installed first.
MCRGB - A Colour Picker for Blocks is a free Minecraft Java mod. Compatible with Minecraft 1.20.1, 1.21, 1.21.1, 1.21.11 and newer. Downloaded 7,873 times (via CurseForge). Download it and open it directly in the game.