I tried to put just the prompt symbol in yellow ">" (and not the whole line) and I didn't succeed. Don't bother with that, it's just a detail, but if there's a simple way to do it.
strings {
yellow_prompt : string "<>><6>>" ;
}
system_messages {
prompt = {yellow_prompt}
}
I tried also to cheat using prior_prompt but it displays a new line after it.