[villagetinker]

OP, I think your original question was about the color of the SCREEN material, so I will address that.
First I agree with the comments about using the bronze-colored aluminum, the STEEL screws used to assemble the framework will rust of time, and the discoloration on the white aluminum is very noticeable, while on the bronze it tends to blend in.
Now as for the screening, I have never seen the light colored screen on a bronze enclosure, but have seen it many times on a white enclosure. As for the lifetime of the screening, you would need to talk to any of the several companies that do the screen work, I have A+ screening, and Todds over the years, in any case I would expect to get around 10 years before the screening needs to be replaced from normal wear and tear, sooner if we get hit with a hurricane (been there done that).