Color to UVW is used to transform the coordinates from one of the other projection nodes using texture operators. That is, a projection is converted into a texture using UV coordinate, then transformed using texture operations, and converted back to a projection using Color to UVW. One example would be displacing textures in UV space using another procedural texture, such as the image below, where the main texture is a Checks map and a Fractal Noise is displacing the UVW space when the material is applied to the mesh object.


Color to UVW


Figure 1: Displacing a Checks texture with a Fractal Noise texture using the Color to UVW projection node


The Compatibility mode has options for Default and 2021.1 where the u-axis is inverted when used as an input to an environment or emission distribution texture.