A problem at work arose: how can we set all the LCD displays of the five new products to be the same color? Setting them to the same PWM values leaves them looking noticeably different due to differences in LEDs.
At first we bought [$$$] a color tester but it didn't serve our needs. Most color testers use a bright white light to help the sensor module. In this case, the white light washes out the LEDs of the backlight and outputs the same value no matter what it actually looks like.
A solution I created is this LCD Color Calibration Tool. It looks at the backlight color and outputs an RGB value. This allows manufactuering to set the background color consitently by matching the RGB values.
The APDS-9960 color sensor is used for this project. A TFT LCD and Feather M0 from Adafruit was also used. I designed and printed the enclosure and jig. The code is just a quick and dirty hodge-podge of Arudino examples.