You can use an effect arrow as a paint brush with paint. : r/Minecraft
WorldEdit Guide #6 - Beginning with Brushes - YouTube
1.5.2][Forge] Magic Paintbrush Mod 1.0.0 - The world is your canvas! - Minecraft Mods - Mapping and Modding: Java Edition - Minecraft Forum - Minecraft Forum
Paint Mod! Tap or shoot paint! - MCPE: Mods / Tools - Minecraft: Pocket Edition - Minecraft Forum - Minecraft Forum
How to make a paintbrush in Minecraft - Tutorial - YouTube