Ok!First off,our little doobie needs eyebrows.Best for expression in my experience.
Of course,there could be different colors for diffrent "dooblets" or even doobie families, so one family could be pink, one blue, one green,etc.
And dooblets can be distinguished by say one having an odd swirl of hair,one with glasses,one with a flower on her head, etc.Eye color changing could replace the original idea for the expression.
And finally, morphs for the eyes.Say swirly for dazed(say after a concussion),heart shaped for in love,exclamation point for shocked,another etc.
It is your project, these are just suggestions.