I'm aware of the Firefox Feedback Addon's use of colored emoticons to emphasize emotions, coding it with color in addition to shape, but I think those are actually a bad design that shouldn't be repeated. To the credit of the MoodBar design, at least it used more mute tones so that black could feasibly used for facial features - the white facial features Firefox used make the emoticons appear non-human. Unfortunately, using the more mute colors causes them to be closer to Caucasian skin tones, making them appear to be more litteral than figurative colors being applied to a human. Colored skin tones such as these are seen in cartoon art, where the most conventional meanings aren't quite what is intended to be conveyed here - specifically green suggests poor health and red suggest anger. Perhaps we could consider using more common emoticon artwork, such as tango icons which use a yellow skin-tone that's vivid enough to be of nondescript race, but also light enough to allow black to be used for facial features, ensuring the emotes look human. Obviously this set does not include a confused icon, but one could be built from the available SVG files and following the Tango style guidelines.
This post was posted by Trevor Parscal (WMF), but signed as Trevor Parscal.