If your stroke is 7 subpixels wide, it will be, for instance, RGBRGBR. That has three Rs, two Gs, and two Bs. That is 50% more red light than blue or green. That is tinted red, no matter how you look at it.

Subpixel antialiasing does distort colours. That is just a physical fact.

The only reason it works at all is that on average, it will even out to a uniform white. But in the details, it will not. Especially around straight vertical edges.

That's a very naive and wrong way to do subpixel-AA. Roughly, to calculate the light intensity of a red subpixel, you must also take into account the red light intensity around a whole pixel area around that subpixel, centered on that subpixel. There are better filters to use here, this would be a box filter, which is 1-pixel wide.

No, it is not. It is the physically correct way to do it. 50% more red light is emitted than blue or green. That is a red tint. Your eyes aren't going to see that as anything other than a red-tinted line. That is what you will see. Sub-pixel antialiased text looks like it has colourful fringes. People see this. It is not in their imagination. It actually is there, and it is exactly because of sub-pixel antialiasing.

>No, it is not. It is the physically correct way to do it. 50% more red light is emitted than blue or green. That is a red tint.

That is a red tint. And that's why it's not the correct way to do it. A subpixel antialiased white line that is seven subpixels wide, on a black background, should not produce (8-bit RGB triplets): 0-0-0, 255-255-255, 255-255-255, 255-0-0.

Then that means you can not render full white.

Full brightness white is supposed to be reserved for light sources anyway, definitely not text background !

I’m not agreeing or disagreeing with any of you as I don’t have enough knowledge on the topic, but what you say would effectively mean that there is no other possible color besides RGB, which is technically true, but is a nigh useless distinction as color blending is a real phenomenon that happens to human vision. In this way, subpixel hinting, while a hack with quite a few tradeoffs, just hijacks color blending used for producing color normally on your screen for sharper fonts.

> but what you say would effectively mean that there is no other possible color besides RGB

It would not at all mean that? I don't know why you would think it means that.

All I am saying is that a if you draw a vertical line 7 subpixels wide, the light it emits will not add up to white. This is a simple physical fact.

To make it easier to imagine, think of a one subpixel wide vertical line. It will be either pure red, pure green or pure blue depending on position. In no way will that ever look white.