@Zeetrain you need to not only lok at teh wattage but more importantl for plants look at the spectrum - Essentially its the coloration the light gives off and plants thrive better in bluer lights then in yellow-red lights.
@JMILLER I think you seen my Ludwigia in the 55g Diary thread hadn't you?
What I noticed is that the plants closest to the spray bar / outlet of your filter are THE most vivid colors. So check if there's a way for you do plant yours closer to the output of your tank. Don't ask me why they do this - But I can tell you they just do
Also important is the spectrum; they reflect the light they receive if you will. Now if you have super high end blue or maybe even purple lights (anywhere from 7-8000K) they won't be too red. If you have lower Kelvin rated lights (I'd have to look again I think my 55g gets 5800K) there's more red in the mix of light for them.
Hoep this makes sense and I didn't confuse no one right now.