Tutorial written ages ago on dark maps.
http://twhl.co.za/tutorial.php?id=43This should be pretty much what you want, however to make it just a tad bit orange will take a lot of trial and error. In my experience I never got an orange light_environment to look quite right. The in game threshold between red and yellow is
very limited in terms of being able to distinguish the difference.
The midground I found is ok-ish, but you'd need to find a cl_skyname that would go with it. You can try this and see how it looks in your map:
map -> map properties -> cl_skyname: night
light_environment setup:
pitch: -60
brightness: 222 46 1 1
This should be all you need. If this is too dark for you, increase the
last number ("1") to something higher (like 2 or 3). Any higher and it'll get bright real quick.
If you want something darker there's not much you can do short of using orange colored texture lights only.