To add to the info. If I switch the graphics card automatic switching of,f the screen goes to the blueish hue regardless of the software that is running. So it is a graphics card switching issue. Nothing at all to do with Aperture or FCP.
I'll be spending some time on one of the other forums to get to the bottom of this. For now switching off the automatic switching followed by a restart, then turning it back on gets it working correctly it appears. But for how long ???