Newly excavated colored cultural relics often suffer color fading or changes when their environments change suddenly, which affects both their safety and artistic qualities. In order to study the various factors that affect tomb murals after they are exposed to the external environment, site monitoring was conducted to measure chromatic aberration and surface water content in the tombs. Identical red,yellow,blue and black colored areas of the tomb murals were studied. The results show that the color change is closely related to the surface water content. The micro-Raman spectrum results show the red pigment is HgS, the yellow is α-FeOOH, the blue is (Na,Ca)7-8(Al,Si)₁₂(O,S)₂₄SO₄ and the black is C. We found that the color change of the tomb murals was caused by the water:during the early excavation stage, the humidity of the murals was high and the colors were bright; but with the drying of the murals, the color saturation degraded and the murals became lighter in color. At the same time, migration of salts onto the surface also caused the murals to become paler in color.