This is an example on the behaviour of two different fade effects, first one without the modulate flag and the second one exactly the same but with it. If you don't know what modulate is this is deeply recommended for you, the flag has a very good effect.
Edit: Fix'd error with .bsp file. You should now see the effect without problem.
don't worry i'll just fake it
modulate may just be the effect i need. I like those pipebomb shaped lights.
anyway I fixed it.