The Phantom Troubadour
Revenge-driven costumed murderer in the "Troubadour of Terror" story in The Human Torch comic book, vol. 1, #31 (July 1948). His real name is name David Larnum. He murders musician Vladimir Borsch, violinist Leo Briggs, and tries to kill married couple Jim and Luella Clegget.
Shortly after co-writing the tune "Death in Venice" with the above musicians, Larnum was in a shipwreck and was presumed dead by his co-composers. They published the song in his memory, and it became popular. However, unbeknownst, Larnum survived on a deserted isle for some years before making it back to the mainland. Learning of the song's success, he assumed they all stole it from him, and vowed revenge.
And also vowed to dress up like a color-blind idiot in a bright yellow shirt, green plaid pants, a red cape, pirate boots, and a floppy hat with a big feather sticking out.
When Larnum comes for the Cleggets, they try to explain to him that he's murdered two people on a wacky misunderstanding, but he goes ahead and tries to murder them anyway.
Aquatic superheroes Namor and Namora stop him.
The song's title, "Death in Venice," is taken from the 1912 novella of the same name by Thomas Mann.