International interlaboratory test results show significant fiber color effects on differences in strength measurements using Stelomer and HVI. Dyed fibers were used to evaluate the effect of fiber color on the optical mass measurements made by HVI systems. Cottons were dyed to within the Rd and +b ranges of the cotton colorimeter chart. Significant correlations were found between color parameters (Rd and +b) and weight estimations based on optical readings. Corrections are possible to minimize the effect of color in optical mass measurements.