Suppose I have a noise texture and I want to take the output as the input to a color ramp. I've seen tutorials where the factor is inserted into the color ramp's factor input, and I've seen tutorials where the color of the noise texture is used instead. Why would I want to use one over the other? What are the use cases?
On the Noise texture node, Factor is a number from 0 to 1, whereas Color is a three number set, all of which range from 0 to 1. If you input Color into a Factor socket like the one on the Color Ramp node, it will average the three color channel numbers and turn it into greyscale. If you wanted to get three semi-related random values together, you could use the Color output and split it with the Separate RGB converter node. Or if you wanted semi-random “fluffy” color, of course, you could use it without splitting. For one Color Ramp node, however, I would just use Factor.