On your display a pixel appears as a narrow sorta-rectangle, with a bit of black space above and below, and a whole bunch of empty space to the left and right (

On your display a pixel appears as a narrow sorta-rectangle, with a bit of black space above and below, and a whole bunch of empty space to the left and right (populated with 2 other pixels of other primary colors). But properly doing antialiasing for the precise geometry of sub pixels is going to be a big pain in the butt, and will be device specific and break down hard when you get to a device that uses a different pixel geometry, or when someone applies intermediate processing to your image before display. Not to mention, if you really want to get it exactly right, you’ll need to take into account the viewer’s visual acuity, the viewing distance, and the precise color characteristics of the display and surrounding environment.