In general, the 'gain' of a camera refers to the amount of signal amplification between the CCD output and the A-D output. In most cases, this is set so that a 'full well' pixel just causes an output of 65535 (saturation) from the A-D. This is to optimise the dynamic range and is not associated with the QE of the device, as the wells will overflow at this same A-D value with enough exposure time, however long is needed.
In the case of the MX7C and MX716, the full well value of the chips is the same and so the electronic gain is the same. Any difference in QE will be seen in the difference of required exposure time to achieve the same A-D output level. As a rough approximation, the CMY filters lose about half of the visible light for these pixels, while the G filter loses perhaps 3/4. This makes the 'visible' sensitivity of the MX7C roughly 1/3 that of the MX716. However, the filters become relatively transparent in the near IR, and the chip has a lot of IR response, so if no IR blocking filter is used, the overall response of the MX7C rises significantly higher than the estimated 1/3 and may reach about half that of the MX716.