Comment by layer8

I didn’t quite get that either. It seems to be based on the fact that the intensity of sunlight varies with frequency: https://sunwindsolar.com/wp-content/uploads/2013/09/insolati.... Green in the middle of the visible spectrum is the most intense, whereas blue and red fall of towards the edges of the visible spectrum, so are less intense. Maybe the noise is less for blue and red merely by virtue of those frequency ranges having less intensity.