This was a trick back in the computer hooked to your TV days. There was a higher resolution mode on my Tandy color computer. It was black and white, though. But if you alternated positions properly you could also have solid red and blue fills.
I’ve lightly dabbled into subpixel art, sorta.
In my experiments, each full pixel still takes 3 subpixels, but…
If you drop a white pixel at X coordinate, it renders 0xFFFFFF on the RGB subpixels.
But drop a white pixel on X+0.33, it renders on GBR.
Drop a white pixel on X+0.67, it renders on BRG.
All three are valid white full pixels, just offset by thirds.
I guess that would more appropriately be considered ‘fractional pixels’ or something though. Still neat that if used properly and creatively, it can yield higher resolution graphics, of sorts…