i used to buy nail polish like crazy, until i discovered that out of about 50 bottles i had lots of slight variations of essentially these same few colors over and over again:
sort of a dusty mauve (which i call granite)
sheer pinkish white
and then the occasional impulse - a bottle of bright orange or teal or something that just didn't fit in.
(incidently, these color swatches are of sephora nail polish, which i haven't tried yet.)