4 diamino 2 3 diphenoxyanthraquinone color index 62025 makrolexrotviolett r or makrolexblau rr 1 4 bis 2 6 diethyl 4 methylphenylamino anthraquinone or 1 8 bis 4 methylphenylamino anthraquinone the expression 34 organic dyes 34 as used in the context of the invention is also intended to include organic metal salts which comply with the above mentioned requirement with regard to the absorption maximum such as cobalt naphthenate as these are also suitable for use in accordance with the invention the quantity of dye to be added to the starting polyisocyanate depends upon its color and upon the particular type of dye used and generally amounts to between about 0 01 and 1 ppm preferably between about 0 1 and 0 6 ppm based on starting polyisocyanate the optimal quantity is best empirically determined by a few preliminary tests the dyes may be added to the starting polyisocyanates or their solutions in solid or dissolved form in which case the solvents mentioned above or even triethyl phosphate for example may be used in the second process for producing the substantially colorless polyisocyanates according to the invention the dyes are incorporated in the starting diisocyanates or in the auxiliaries used for their modification before the actual production of the modified lacquer grade polyisocyanates thus it is possible for example in the production of biuret polyisocyanates based on 1 6 diisocyanatohexane to incorporate the dye mixture in the 1 6 diisocyanatohexane used or.