an instrument for determining the intensity and hue of a color, as of a solution in chemical analysis, by comparing it with standard colors
See colorimeter in American Heritage Dictionary 4
(kŭlˌə-rĭmˈĭ-tər)
noun
Any of various instruments used to determine or specify colors, as by comparison with spectroscopic or visual standards.
An instrument that measures the concentration of a known constituent of a solution by comparison with colors of standard solutions of that constituent.