Constraint some method of thresholding give result of quality of less grey-scale as according to original colour wight visually. hence needed by study to get method of thresholding correct trough approach of colour model approach. research methods is development of tresholding with double hex cone model. through this model is got by 8 colour dots base and from 18 joint colour among dots base which the ach the joint there are 3 selected colour with same intensity interval distance. the colour compiled in matric 24 x 25 beetween value of luminancy and of hue. grey-scale colour data to generated through printer option and PDF format by its colour values in the form of data tables. data column show sequence assess hue with interval distance is 10 from 0 up to 230 and value of luminancy from 0 up to 240. forming of algorithm and equation yielded to through approach of diferensial polinominal interpolation divided newton. and practically got by coefficient and interpolasi yield equivalent colour and both more according to visually in comparing average method result of division of primary colour.