Rainbows are the "in thing" at the moment...mainly because I have a 7yo who likes rainbow, gold and silver colours the best.
That's why I made the best friend a birthday card using a rainbow background.
The rainbow background was made by painting with bright acrylic paints. Then, it was cut with a die by Paper Roses (19097 Poppy decorative background metal die). I filled in only the flowers by paper piecing with white card. The sentiment comes from a Kaisercraft paper pack.
Do you want something in rainbow colours for a special youngster? I'm happy to look for design ideas for you, and I can easily personalise it with names and special messages.