Additives and Lighting!

Ive been making a map for the last few days now and its sort of a modern training facility theme. And I made these lights that line the bottom on the floor that you can see here in first screenshot. (The white lights at the bottomish area)
http://img390.imageshack.us/img390/1971/pic1bw6.jpg
(There are no white lights in this room or in the entire map, its just the additive lighting that is far too bright)

I made the original texture nomal func_wall and then made a copy of it that is slightly larger then the original and made it func_wall but render mode is 'additive' so that it becomes bright and makes the lights appear much more radiant.
http://img266.imageshack.us/img266/6825/pic2yj2.jpg

But the problem is no matter what opacitiy I set it to, it emits far too much white light from the texture, ass you can see in first screenshot the white light is completely taking over the red lights which is supposed to be the main colour of that area!

Can someone explain to me why the additive light is way too bright and wont scale down with the lower opacities ive been setting it to. Currently its 50/255 and its same light that came out of 150/255.

Hopefully someone understands my situation and can tell me! Thanks
[ Edited ]