A painted cardboard rainbow instantly adds an undeniable splash of color when used as a backdrop or prop for a theatrical performance. It can also be implemented into a birthday party theme as an element of decoration.
Decide how large and thick you want to your rainbow to be. Then draw a half circle arch onto the cardboard sheet accordingly. There are seven total colors in a rainbow. If you plan to use the rainbow as a prop for the theater performance, all seven colors should be visible not only to viewers sitting in the front row, but to those in the back as well. Take this fact into consideration as you are deciding what size your rainbow should be.
Cut out your arch. Space out the thickness of your arch to encompass all seven required rainbow colors. If you are particular about each color of the rainbow being the same width, you may use a ruler to divide the available width into seven equal sections. Use a pencil to draw additional arched lines.
Paint your rainbow. The top-most arch on a rainbow is red. Directly beneath should be orange, then yellow, followed by green, blue, indigo, and violet. This is the exact order of the color spectrum contained in any rainbow. Even if you want your completed rainbow to possess a whimsical character, you should not stray from this specific color order.