The earliest traditional colors for Easter eggs were red and green, btw. Red is the most ancient sacred color, the color of life energy. Green of course is also symbolic of life and vitality and renewal. Pastel colors became popular later, probably in imitation of the pinks and yellows and lavenders of Spring flowers. Supposedly teal is the "hot" color this year!!
Here are some links ~ have fun:
http://www.floridaherbs.com/Newsletter_Archives_Dyeing_Easter_Eggs.htm
http://www.organicconsumers.org/school/eggs060405.cfm
http://www.aeb.org/kidsandfamily/eastereggs/naturaldyed.asp
On that last link, you'll want to click the "next" button at the bottom a couple of times, because the next few pages have wonderful ideas for decorating eggs with stencils, leaves and seeds, ribbon, even postage stamps!
The vintage egg greeting card pictures are from
Lunagirl Victorian Holidays & Occasions.