[Russianeer]

Need some kind of render function to perform this. Tried many different things with

SetEntityRenderColor

and

SetEntityRenderMode

nothing seemed to work.

Are there any other options I can use?

[Silvers]

This works for me in L4D2:

SetEntityRenderMode(entity, RENDER_TRANSCOLOR);
SetEntityRenderColor(entity, 255, 255, 255, 128);

Where 128 is the opacity from 0-255.