If the light is constant across the court changing lenses is not going to change the exposure on the court. Your meter can be effected by different colors because those color reflect light differently but you shouldn't change your cameras exposure. You could walk down on the court before the game and take an incident meter reading and as long as that light doesn't change, that should be correct exposure no mater what lens or camera you are shooting with if the lenses and the cameras are working correctly. Things like color and different type of reflectance off surfaces can effect your meter thus giving incorrect readings.
The best measure is off the floor completely agreed. One thing that directly impacts exposure are the painted areas on the floor - the key and the usually painted logo area in the center. You usually see this in the shadowed areas getting deeper in and around the key.
But you also have the effect of the overhead lights. When you use a very tight shot, you are getting little impact from the overhead lights. But in arenas like the Old NC State with a wide angle - or others that particularly use rim lighting, you start picking up direct light - not just reflected off the subject. The impact to the photo varies. But what you typically end up with is you don't deal with it is usually blown highlights or deep shadows. Unfortunately the price is loss of contrast. But that is a lot easier to fix now days in photoshop rather than like in the old days applying contrast filters.
Anyway, photography is 1 part science, 1 part emotion, and 1 part experience. The science part of it makes people feel comfortable - much of the reason I gravitated to the photojournalism side of things. But experience is what helps us when what should work right logically, doesn't. Experience is also what tells us how to shoot into the light when the light meter tells us something different. T-stops were invented because f-stops aren't always right. Anyway.... enough on this. Cheers.
