Bluser is more likely a blue version of bowser.
He hates every other color that isn't blue, and 'automatically' hate someone that isn't blue. He do like people that are blue, like Geno.
He is a boss in Glitchy's adventure. His HP is 1000, and his psychopath message is 'Mhhh! Foolish colorful rivals!!'.
SMG4 is blue, and it don't make sense, since Bluser hate him, even being blue.
He have few appearences. None of these he was the main antagonist, only in Blue doomsday.
His spikes sometimes are blue.