You likely could but you would have to re-reference the output from the device which would make it not much fun to use. I have thought about making a container with a tri-colored LED and a photocell, essentially a cheap colorimeter, driven by a Arduino microcontroller. The sample would go between the LED and the photocell, the microcontroller would then cycle the red, green, and blue LEDs on measuring the transmission through the fluid to determine the RGB value for the fluid. This then would be referenced to the color tests. Once referenced you could enter the color vs (test material concentration) functions into the controller. The largest issues are that the RGB LEDs only generate the appearance of full spectrum, if the color of fluid is between the frequencies of the LEDs it might appear transparent which is why Hanna may have multiple models. Normally you would only need one proper colorimeter for all the tests using colorimetric methods. Unfortunately my interest is only exceeded by my lack of motivation. I hardly test my water anymore.