Also, if you have bright user-interface elements in your view your eyes accomodate to include that level of brightness. The same goes for your immediate computing environment, playing in daylight ruins your perception of dark silhouettes (sp??). I often play in a dark room with true red light (battery powered LED) to allow me to see my keyboard.
You could disable the message panel (numeric pad Del/point button) if you are in bridgeview (F4). And avoid switching to the map or use the fairly white course compass of GWX. But if you use views like the periscopes/UZO with bright interface elements then you may need to customize (mod) the brightness of certain game graphic files with an editor. But that is easier said than done. Or just use a mod that allready is a 'dark'-mod, like OLCs GUI(special).
In regards to your 'white contrast' solution and seeing things in the dark. Forget that! If seeing dark things in Sh3 is a priority you don't want ANY white, but rather grey. (but other uses ofcourse you do, so try to find a way to change color/brightness
profiles easily in your videocard settings) Make contrast as low as possible and increase brightness until you start to see something in the darkness. Test it using a screendump where you know your crew spotted something. (to not be cheating in relation to your crew)