Pros:

Colors! :D :D :D
Makes the game better in general.
Zombies don't look like goth teenagers anymore! :D

Cons:

It seems like they don't work on L4D1 maps, but that might just be lighting.
Hmmmm....... I guess there is nothing else.

Conclusion:

Very nice mod! I am going to use it for now on. Download this if you haven't.