Hello,
I really need help with a choice for pastel colored dress for an occasion. The problem, I don't know what pastel colored means

Pink, light blue, sage green, spring green, tan, light yellow.

Pastel colors are the more subtle shades of any color, they are never bright...

http://fob.po8.org/files/images/pastel.png

Thank you, you guys that's really helpful.

A shade is mixed with black, a tint is mixed with white
Pastels are tints of any color