Extensive Tests: Hardware
In a previous circuit, I used a 2-bit opto-isolator limited to 4 colours.
I went further with an I2C remote 8-bit I/O expander, opening the transfer for up to 256 colours. Those 256 colours are a meagre slice from the total capacity of the sensor with (2^10)^4 possibilities.
The circuit I've built uses 4 ports for transfer and 4 ports for monitoring with LEDs.