[Animats]

It's not a CRT thing, it's a NTSC thing. He seems to be trying to emulate NTSC (analog broadcast TV) color, not RGB. NTSC color signals have much lower bandwidth than the intensity signal. You can only go through the entire color gamut about 10 times across the width of the screen. So, for NTSC emulation, you should convert each scan line from RGB to YUV, then low-pass filter the UV component, then reassemble. You'll now have sharp edges where the intensity changes and fuzzy edges where the color changes, just like crappy old NTSC devices. This is strictly a horizontal phenomenon - in the vertical dimension, adjacent scan lines can be completely different colors without artifacts.

[6502nerdface]

I think TFA's also trying to emulate specifically CRT-related effects like phosphor glow/trails. Maybe sort of conflating NTSC and CRT effects into one "CRT simulation"