What Type Of Rainbow Did Cleopatra Die On?

Hey guys, I am doing a school project on a Shakespearean character. In my English class, we are reading Julius Caesar, and in one quote, Brutus says, "Cleopatra so sweet she hath die on bows rains." I was wondering if she actually did die on a rainbow, and if so, what type of rainbow might that be? Thanks a lot! xoxo!