The color of roses, when given, symbolize something specific:

Red roses say "I love you," as most of us know.
White roses are given to someone adored. They symbolize reverence, innocence and purity.
Yellow roses are meant to reflect joy. (Good for birthdays and new mothers.)
Coral and Orange roses express desire.
Pink means grace and gentility.
Red and yellow roses together say congratulations.
Red and white are supposed to symbolize unity.
Pink and white are meant to be a sign of enduring love.
Two roses intertwined stand for an engagement.