A couple of things with this. Swiping away notifications won't stop the led at the moment: vote for this android feature request here: http://code.google.com/p/android/issues/detail?id=23106
Also try adding the light flow debugger widget to a homescreen as that will tell you which notifications it thinks are on.
As for battery drain, I think it varies for different people depending on what settings they use. I try to set the default app settings to be fairly sensible on battery drain.
---------- Post added at 06:31 AM ---------- Previous post was at 06:29 AM ----------
I'm planning in a future release to have a section where you can remap the preset colors to new RGB values as it's one of those things that varies a little from phone to phone. The colors were originally based on what the nexus one could manage (it was probably the best phone for color representation) and then tweaked a little for the galaxy nexus.
As I've not seen a nexus 4 (stupid google play checkout errors) yet I've not been able to experiment.