You can model the performance yourself using a freebie download from the Lawrence Berkeley Nat'l Lab fenestration folks:

http://windows.lbl.gov/software/resfen/resfen.html

Since it's zip-code specific (there are seven different location options for FL), it is modeled using actual historical weather data for the location, minimizing the guesswork involved. It's not the slickest piece of software out there, but it's not a total pain either, with a bare-bones user interface. If you insert your actual utility rates it'll give you an estimate of actual operating cost, if you need to fine tune the cost/benefit analysis rather than answer "will A outperform B" type questions.

Simonton has a "driftwood" finish in vinyl, which isn't really dark but it's darker than white or beige. It's sort of a middle value in terms of color. Doesn't Florida have very specific testing required for window manufacturers? Not all brands are certified there.