The phrase "you're on" is typically used as an indication that it is someone's turn to perform or participate in something. However, there are several other synonyms that convey a similar meaning, such as "it's your go," "your move," "you're up," "your turn," and "proceed." Additionally, if you are looking for a more casual or humorous way to indicate that someone is next, you could use phrases like "step right up," "time to shine," or "show us what you've got." Regardless of the phrase used, the idea is to indicate that the focus is now on the person who has been called upon to act.