<p>A system can comprise a memory to store machine readable instructions and a processing unit to access the memory and execute the machine readable instructions. The machine readable instructions can comprise a press color state (PCS) estimator to calculate an optical density for each of four single separation solid colors based on a color measurement provided by a scanner. The color measurement can characterize material printed on a substrate and scanned by a scanner. The PCS estimator can also provide an updated LUT for each of the four single separation colors based on the color measurement provided by the scanner. The machine readable instructions can comprise a print controller to provide the optical density for each of the four single separation solid colors and the updated LUT to a printer to facilitate color calibration of the printer.</p>
