Referring to the graph "The Continuous Spectra of Stars: Brightness of Emitted Light Versus Wavelength" on page 451, you can see the overall trend is that as the surface temperature of a star rises, the brightness of the emitted light increases and the peak of the curve moves closer to the blue end of the spectrum. So, if a star produces light that is less yellow and more white than the light emitted by the Sun, the surface of this star must have a higher temperature than the surface of the Sun. Similarly, if a star produces light that is more orange than the light emitted by the Sun, the surface of this star must have a lower temperature than the surface of the Sun. simplify to a short sentence