You can use a CD or DVD to view the color spectrum of your light sources ...

MICHAEL ZHANG, PETAPIXEL:

"If you want to view the color spectrum of a light source in your studio, there’s actually a super cheap and easy way to do so: an ordinary CD or DVD can do the trick. Simply allow the light to reflect from the surface of the disc into your eye — it acts as a diffraction grating, allowing you to see the different color bands in the light."

Learn how to do it right, through a video demonstration, here.