colour wheel

plural colour wheels · alternative US color wheel

1. UKA 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, Robert Jeschonek, Christmas at Glosser's, page 13

   1 more example

   With fears that draping normal Christmas fairy lights through the tree's aluminium branches would cause a short circuit, the trees were lit from below by a rotating colour wheel divided into wedge-shaped segments of variously coloured plastic.

   2013, Martin Pullen, The Completely Useless Guide to Christmas