Why purple and yellow ?

Can someone pls. tell me why the colours purple and yellow are associated with Easter? At least, that's what I associate those two colours together with. (bad sentence, ending in a preposition -- Chris, do not repeat this to your students :)) O.K., I'm waiting...
Now you may ask me why the question christine? Well, I was just washing one of Ben's Tommy Hilfiger dress (why are they called dress?) shirts that besides he does not want me to wash but would rather he dry clean but I tell him, all those chemicals -- yuck! -- anyway, there you have it, I was washing a pinstriped purple and yellow shirt and thought of our upcoming Easter.