Curt Home Depot and Lowes told me the same thing. Its totally not true. I have a armstrong drop ceiling with the grids and they cost the same as the white ones at Home Depot. Here is what I did. Go to the Armstrong web site and get there customer service number, ask them for a distributer in your area and call them directly. If you have any problems feel free to email me for some more info.
By all means you do not have to go through the trouble of painting grids and tiles.
If you want take a look at my ceiling tiles, the are Armstrong factory black
MY THEATER
Jared