Thought I'd have a try at the editing the file myself... eek, linebreaks please! What a mess that lua file is atm - the others seem fine but that one has no linebreaks and just a wall of text. I even reinstalled the addon to check it's not my Notepad breaking stuff but it doesn't seem to be my end
Anyway, colours. White works well enough but I guess it looks a tad bland, so onto others.
Pale grey 0.9, 0.9, 0.9 works ok and doesn't look like anything else:
Couldn't really get a pink that didn't look too pale and a bit odd, else too near whispers, best of a bad bunch was 1.0, 0.7, 0.9:
Alternatively, this pale green 0.5, 1.0, 0.7 gives a nice visual gradient through the messages:
Think I like the green the best but the grey's fine too, not so keen on the pink though, looks a bit messy with too much difference in the colours.