In Red Starved Marceline was ravenously hungery and in a beast-like state. I imagine that if she was in he normal frame of mind she would likely be much more conservative in her consumption.
As well, in Red Starved we only see Peebles for about a minute after being sucked. It's entirely possible that she regains her shape before her color.
As well, in Red Starved we only see Peebles for about a minute after being sucked. It's entirely possible that she regains her shape before her color.