From left to right: Zip, Arty, Bif and Prof.
The Colour Underground is a organization that was formed to recolour Chroma City after Comrade Black had taken control of it.
Its leader is the Professor and its main members are Arty, Zip and Bif. Blob and Pinky are also members. There are also some unmentioned members as some rescued Raydians in de Blob 2 (DS) claim themselves to be members. Other possible (but unconfirmed) members include Reggie who appears in de Blob 2 (he can be seen wearing a hat with the Color Underground symbol on it), an unnamed sporty looking blue Raydian and an unnamed green female Raydian who both give mission objectives in de Blob Revolution.
Blob does most of the hard work, recolouring the city and the other members make challenges to co-ordinate Blob in his mission. They also teach Blob what he needs to know, as well as give out missions.