generally aura's are tied to current emotions
im gonna take a guess at some here
red - anger, lust
pink - passion, love
white - clear mind, steady flow of ones self
black - obviously nothing good
grey - sad, neutral
yellow - happy,, joy
blue - content, aware
green - neutral, earthly
purple - sad, depressed, scared
orange - confident, beaming, sure
thats all i can think of at the moment. and these are just my guesses. some of the emotions i didnt know how to sum up, like "earthly".
anyways, hope this helps.