The development of durable daylight fluorescent retroreflective sheetings has led us to investigate same of the factors that influence color measurement of these materials. The colorimetry of retroreflective materials is particularly sensitive to measurement geometry. The added aspect of fluorescence increases the spectral uncertainties, making appearance measurements even more difficult. The visual properties used to describe fluorescent retroreflective materials should include chromaticity, lightness, peak spectral radiance factor, nighttime color, and color stability on exposure. A number of test methods exist for these measurements. however, practical experience in applying these methods to fluorescent materials shows significant variation in the resulting measured values. Colorimetric measurements on commercial instruments using 45/0 (0/45) geometry, a stimulated D65 illuminant, and the CIE 2 degrees standard observer yield results that are inadequate for precise quality control of durable fluorescent retroreflective materials. The uncertainty can be reduced by the use of transfer standards, provided that the standard is similar to the sample in both hue and fluorescent emission. Ultimately, the wide availability of commercial 2-monochromator spectrocolorimeters will be required.