Two invariance properties concerning object color changes under daylights are discussed. The first is the invariance over object variety. Color changes under daylights with various correlated color temperatures were simulated using the Standard Object Colour Spectra Database (SOCS). It was found that the color changes do not depend on object categories. When we changed the illumination from D50 to the 9,300K CIE daylight, the tristimulus values of possible metamers under D50 were found to be very similar under the 9,300K daylight. It means that the metameric relation is very stable under daylights. The second is the invariance over the correlated color temperatures of daylight. The color change trajectories in the tristimulus space are almost stable even when the daylight color temperature is different. In addition, the degree of color changes is almost constant when the color temperature is measured in ‘mired’. This result quantitatively justifies the conventional use of color conversion filters in the photographic industry. These invariance properties should be useful for simple realization of color constancy ability found in human vision.