Residual lignin in unbleached kraft pulp and unbleached pulps from CEHDED stages correlate well with the color values of the same materials of known CIE L*. a*, b*, C* and h* values. L* and C* values of pulps were evaluated to estimate their residual lignin. By using L* and C* values. an equation enabling an on line-control of the bleaching parameters could be established.