reactive red 180 c i reactive blue 19 rb 19 c i reactive blue 20 and c i reactive blue 21 rb 21 it is important that the first compound hydrophilic vinylic compound and the second compound reactive dye should be well dissolved in the water these two reactants should form a homogeneous aqueous solution before and after the reaction most importantly the resulting reactive tinting compound should be completely miscible in the lens forming materials before and after cure to prevent the lens defects such as uneven shade of color or inconsistent tinting color from batch to batch in synthesis of the present reactive tinting compound the conditions can be modified according to the type of the reactants although many dying assistant chemicals such as dispersant salt wetting agent fixing agent etc are usually applied in the dying process these dying helpers are not required in the present invention the actual conditions chosen to react dye with the hydrophilic vinylic reactant should be better determined empirically and varied case by case a preparing the reactive tinting compound using a dye with difluoro chloropyrimidine group in order to promote the reaction of the difluoro chloropyrimidine in the dye with the hydroxyl group in the hydrophilic vinylic monomer it is needed to use a base such as for example ammonia triethyl amine alkaline metal hydroxide as sodium hydroxide and salt of alkaline metal as sodium bicarbonate to neutralize the acid by product it is also appropriate to choose a base capable of forming easily removable by product to facilitate the removal of neutralized salt after the reaction the molar amount of the base is added preferably greater than that of the dye to improve the.