Is there a way of inverting all the colours on the screen?

if you have Pro you can render the camrea view to texture, map it on a screen aligned quad, and use a simple pixel shader like:

float4 color=tex2d(entSkin1,tex.xy);
return 1-color;

this ought to do what you want.

or if you dont have Pro you can assign a material like this to every model and level texture.. and then have some variable that toggles between normal and inverted.

I can color shift through the rainbow on panels with a formula. But getting a bmap from the screen and putting onto a panel takes a long time and the colorshifting one is also fairly slow. If you're wandering how to shift hue (colors through the rainbow) with a single number, colorvar going from 0 to 360 in this example, here's the formula:
my.red=125+fcos(colorvar,125);
my.green=125+fcos(colorvar-120,125);
my.blue=125+fcos(colorvar-240,125);

as you can see, the green and blue are simply shifted to the right 120 and 240 degrees making each of the colors equally spaced out for a smooth rainbow transition. You can probably do this with the gamma ramp dll posted by Lion_ts recently.

Or just invert the colors of your textures

OR USE MY GAMMARAMP.DLL
Look at usercontib thread.

FAking an invert using gamma or somehting is not a good solution, becaxsue it would invert everything , include HUD elemnts and so on.. the best solution is to use render to texture, or materials.

Thanx Lion. Your dll does exactly what I wanted.
How would I edit it to "Fade to invert" and back?
Does it do grayscale and sepia?