Maybe I'm not understanding, but the only response I can think of that is red is "Goodbye"... Is that it?
Anyway, if so, it exists down in the results box of the dialogue you are in as a function. you can remove it, but you can't really change it that I know of.
You can make a red response say anything. "Goodbye" is just a standard response that Bethesda used to end conversations.
Anyways,
Edit->Find Text will help you narrow down the dialog entries that use the response you want to change (which Greeting/Topic etc)
Then open the dialog window, find the correct dialog (modded dialog has a star * beside it)
The dialog you're looking for will be in the Results window at the bottom, not in the main dialog line itself.