In the flashback he appears as a block of cobalt with arms, legs, and a face. After getting shattered and trapped in the Mind Scape, his appearance is of a ghost version of himself without legs. 
During his time as a Super Object, he mysterious object who haves the powers of Cobalt Fumes, soon later people around the town went missing and the other find out Cobalt Blue was the one doing this, he was kicked out and he gets revenge.
He very hyperactive, egocentric, aggressive and fastidious.