Just thought I'd tell anyone who's had the same problem the quick and easy solution I found.

I used GIMP to create a small image with a black background (about 50x50). I made a vertical strip one pixel thick. Red on top, then green, then blue, and red again at the bottom. This allowed me to look at each color next to the other. Sure enough, I could see right away that the red pixels were left of both green and blue, and green was left of blue. A horizontal stripe showed no shifting between colors. In addition, a close look at a zoomed view showed some "banding" in the vertical direction for all color, indicating that multiple sub-pixels of one color touch when stacked vertically but not horizontally.