color wheel

noun2

1. •
   A planar circular chart in which related colours are adjacent, and complementary colors are opposite.
2. •
   A device that emits varying colours of light by the use of a wheel, commonly used to illuminate Christmas trees.

   • The twins led him across the room to a silver aluminum Christmas tree in the far corner. A device on the floor cast light on the tree from a bulb behind a slowly turning color wheel. — 2013