Recently I've calibrated my display and it turned the washed out colors in ArmA into a near photorealistic experience, especially in bright sunny days.

I used QuickGamma software to lower the gamma value of my display since the display does not feature such a parameter as adjustable. In quantitative approach it required me to go from 2.2 to 1.8 in QuickGamma. It's built-in test patterns are very small so I used this one http://www.lagom.nl/lcd-test/gamma_calibration.php (opened up in external app, no scaling, no color correction 1:1 ; avoid using web browsers for the purpose).

But to pass the ArmA built-in callibration (configure - video - display; make the cross not visible***) I have to additionally decrease the in-game gamma slider value to 0.7. That's a lot, speaking unsientifically.

***The callibration is well done and indeed for the colors in ArmA to not look washed out it has to be set like this, more or less.