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This is a pretty common behavior with cameras. Different cameras respond to color slightly differently, and the automatic gain and white balance functions of the camera will affect the numeric and perceived color even more.

There is an entire field of study devoted to this topic: Color Theory

I suggest that you do some research into different color spaces (look at HSV for example) and maybe try to find and read a few papers about color tracking in computer vision. Most papers will discuss the techniques that they use to be robust to lighting and other changes in color.