Daylight is 6500K so anything near that really, some plants use different colours in the spectrum more than others but with daylight there's enough of everything.
Okay, thank you! I'm toying between a low tech 1.2WPG no CO2 with my current lamps, (2 x 18w pl), or a high tech 3.7WPG with CO2. I'm able to get a fire extinguisher and 2 x 55w pl lamps (any colour) and control gear for free/nearly free... I'm torn as to what to do!
Just to let you know if your not very experienced growing plants then going with 3.7WPG is gonna cause you trouble, most I'd say is like 2WPG for a beginner but if not then go high tech.