This can technically be done with the current version: If you create a variant of your .png and lower the brightness on it, you can use that as the idle state and it should give the same effect! It does unfortunately require you to make an additional .png though.
However, I'll investigate adding an idle darken effect you can turn on and off (like the "Bounce" toggle) so people don't have to do that and can use one image for both speaking and idle states, no matter what set of .png's they're using.
Good idea, thanks for the suggestion! :)
EDIT: I just made an update which makes this effect toggleable. Let me know if you have any issues with it!
