Technical Abstract: Cotton color is an important classification property. In the U.S., cotton is classified for color using the Uster® High Volume Instrument (HVI). The color of cotton on the HVI is denoted by the parameters Rd and +b, which represent the cotton’s diffuse reflectance and yellowness, respectively. Rd and +b are specific to cotton fiber and are not typical globally recognized color systems. An earlier program established and validated the feasibility of correlating Rd and +b to the globally recognized color system L*a*b* for both standard tiles and cottons. The major impact on agreement between the HVI and standard color spectrophotometers and between color spectrophotometers was the use of glass (required for cotton color analyses) between the sample and the spectrophotometer measurement port. A program was implemented to 1) investigate the impact of glass and glass type on the spectrophotometer color measurements and 2) to determine the feasibility of minimizing the glass impact. The glass impact on spectrophotometer color results was much greater than that of specular component type. The glass impact of the 6 mm thick HVI glass on color results was significantly greater than that of the 1 mm thick microscope slide. Protocols for minimizing glass impacts on spectrophotometer color measurements were determined, with the best overall results obtained with the use of specular component included (SCI) and glass with glass calibration.