Re: [csswg-drafts] [mediaqueries-5] prefers-contrast: infer contrast preference from forced colors (#5224)

Thanks for taking a look at this and adding to the spec. I agree that having some interoperability would be good especially given that we already have some baseline from the WCAG. Ideally, `prefers-contrast` should behave the same across browsers.

To add some context, I went through the Windows high contrast themes that are installed by default and calculated their contrast between text and background colors.

### High Contrast 1 
![image](https://user-images.githubusercontent.com/30676292/88572325-d2459700-cff3-11ea-8dad-009eb268313d.png)
- Contrast ratio: `19.56:1`.
### High Contrast 2
![image](https://user-images.githubusercontent.com/30676292/88572525-281a3f00-cff4-11ea-801d-6eedec7466df.png)
- Contrast ratio: `15.30:1`
### High Contrast 3/4
![image](https://user-images.githubusercontent.com/30676292/88572664-6283dc00-cff4-11ea-817f-9dcab4b1b19c.png)
- Contrast ratio: `21:1`.

Those high contrasts would certainly suggest that a "high contrast" preference is one much higher than the WCAG values. If the inverse is true then perhaps a low contrast is also much lower? It would be nice to get some input from someone who knows why colors like that were chosen and then build a decision about contrast thresholds off of that.

-- 
GitHub Notification of comment by ZekeMedley
Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/5224#issuecomment-664538894 using your GitHub account