The final TCD values (27±33) of the BP type indicator were about twice as much as those (14±15) of MR type. It is generally known that TCD values more than 5.0 can be easily detected by human eyes and TCD more than 12.0 may imply absolutely different color spaces .
The changes in TCD of the BP and MR type indicators showed a zero-order behavior and a typical curve of a square function, respectively, though at the different rate.Thus kinetic approach could be used to model the measurable TCD change of the indicators.