If you are having a hand-fasting, the number of ribbons and choice of colours is up to you. Each colour has a different significance in terms of what you are calling into your relationship.
White: purity, devotion, peace, innocence and new beginnings
Red: passion, love and desire. It is also the color of blood, which is a symbol of life.
Blue: strength, longevity, tranquility, peace, patience and loyalty.