Cross-talk in an RGB photodiode circuit
You should not be seeing any cross-talk. Plus, your schematic is wrong. The sensor is a common-cathode unit, so the circuit should look like







simulate this circuit &ndash; Schematic created using CircuitLab

The fact that your voltages are acting funny suggests that you've done something very wrong. Your schematic also shows no connection to the other end of the power supply and I suspect that that is exactly what you've done. If this is true, your photodiodes are being operated in photovoltaic mode, and this would explain a lot. Please recheck both your power supply polarity and the connections.

If you have failed to make the power supply connection, your circuit looks like







simulate this circuit

and changing one resistance will change all the measured voltages.