The Gaussian Spectrum texture is based on a Gaussian distribution spectrum. Wavelength sets the spectrum's center, and Width sets the curve's width. Narrower widths create purer and more saturated colors.
Figure 1: Gaussian Spectrum texture
Wavelength - This represents the mean wavelength approximation between 380nm - 720nm. Lower wavelength values appear bluish, while higher wavelengths (around 700nm) appear reddish.
Width - Almost no color is visible when using a width of 0.000. On the other hand, a width of 1.000 means the color is spread thin over a large space, and the Texture appears faint.
Power - The Texture's brightness.