Colours was my favourite as a kid and after revisiting it its still pretty great. Its got a greater emphasis on puzzle solving than the other 3D games and while I kinda wish that the game was played entirely in 3D, the 2D sections aren't bad by any means. The soundtrack is also one of the best in the series, with a killer opening track and each world having its own distinct sound makes for a set of really memorable songs. The only real issue I had when replaying is that the writing is so incredibly unfunny and cringe that I ended up just skipping the cutscenes. Gotta love sonic teams 2010s humour