A cool kid with trisomy-21 (Down's syndrome), or someone who has the facial characteristics of Down's syndrome. Someone who looks like they're stoned but they're really not stoned, just zoning out with a mesmerized catatonic gaze, unresponsive to external stimuli.
Dude, you're a total chromostoner!
Dude, you're totally chromostoning it right now!
Whoa! Dude! I can totally see the topography of your lips extruding beyond the horizon of your face! Even at an obtuse angle!