The color of the light being used to expose the film is irrelevant. The density could come from red, green, blue or UV light. The color might affect the contrast or density of the test strips but that would make no difference to the plotting.
Originally Posted by Donald Miller
The key with the plot is that you must have the same measurment of density on the x and y-axis. If not, the curve will be artificially distorted because the units of measurements are of different length on the two axis.