One of the students on our team last year, or the year prior came up with a pretty handy solution.
Open the live feed for the camera in the web browser, aim it at a target have the ring light turned on.
Then use an application like
Just Color Picker. No installer just an exe. It will run on top of the browser which has the video feed in it. Just place your mouse cursor over the live image and record the min/max values for the RGB values that you see in your image. You may need to widen up the ranges to support different lighting conditions.
Your camera should be calibrated prior to running through this sequence.