A color-contrast function is defined in the following manner: CE b(X) = (mx- n050o0) (mx- m ss)o, where a and b refer to two different areas of the lunar surface. Values of this function have been determined for 16 paired areas on the lunar surface at approximately every 100 A in the spectral range 4380 to 6835 A from densitometer tracings of spectrograms having a dispersion of 4.9 A/mm. The results show that there are significant color contrasts, even within the maria. The maximum values of CE(X) lie between and 0W20. The lunar maria seem to be more homogeneous in blue light (below 5500 A) than in red light (above 5500 A). Some of the curves of CE (X) vs X show humps about 500 A wide which resemble lumines- cence bands found by Dubois for various regions of the moon.