it's a pun, すった is grated/shaved and りんご is apple so it messes around the pronunciation of すった (sutta) vs スター (sutaa, which is star or starr in this case)
I think this outfit is because he was trying to dress like a visual kei guy... but if this is the reason he failed XD But yellow is a bad colour in japan XD I think it means that you want to trick someone ^^ So I wouldn't wear yellow in japan, whan I am not as famous as Ringo.
