The Greyscale Color node generates a float value, which node networks use as an input. When connected to a Color input, the result is a greyscale color, with 0 being equivalent to black, and 1 being equivalent to white.
Figure 1: The Greyscale Color node applied to a DiffuseAmount of diffusion, or the reflection of light photons at different angles from an uneven or granular surface. Used for dull, non-reflecting materials or mesh emitters. input