how much light??

Some more questions to consider... What kind of plants is your friend wanting to grow? Stem plants, typically, are fast growers and require more maintenance, but most require medium - high light. There are plants like anubias, crypts and mosses, ferns that don't require much light at all.
Another question -- how much $$ is your friend willing to spend? There's a huge difference in price between T-12 fluorescent, power compact fluorescent and metal halide lighting (the most expensive, but the most intense).
Co2 is good. Just try to get him/her to read about different ways of getting the Co2 into the water (diffusers, reactors, etc) --- read up on rexgrigg.com to start.
Lastly, what are the dimensions of the tank?
Any fish preferences? Some work better with certain plants, etc.
As for the color -- if you mean red plants, some get that way from high light, some low nitrates and a few are just like that under most conditions...
-Ryan

Heheh.

With an open-ended question like this without answers to ringgram's questions...how about 72" Current USA Outer Orbit fixture. 3 x 150W MH + 4 x 96W PC. >

Seriously, once you get ringram's questions answered, we'll be able to give you a better suggestion.

BTW, that fixture is ~$850.

ok
She wants more med light plants-mostly stems and wants to have a variety of color. She wants to keep the costs as low as she can.
She is thinking of several different schools of tetras and maybe some discus.
tank is an all glass standard 180 72"X24"X24"

If she has a wooden canopy on the tank I would highly suggest AH Supply 55 watt kits mounted front to back. The 6x55 watt setup would work quite well. If she wants a bit more light then a 8x55 watt setup should allow her to grow just about anything she wants.

She is much better off to spend the money up front the first time and not fool around trying to save money and getting something that doesn't do what she wants.