Re: [csswg-drafts] [css-color-5] Make channel values in relative color syntax optional (#10689)

We [currently have]():

> If the alpha value of the relative color is omitted, it defaults to that of the [origin color](https://drafts.csswg.org/css-color-5/#origin-color) (rather than defaulting to 100%, as it does in the absolute syntax).

One of those annoying edge cases that still has to be covered: the pointless "do nothing" syntax:

```css
alpha(from var(--mycolor)
```

Options:

- don't allow this, it is pointless. Require alpha always for this form. But this is different to all the rest of RCS
- allow it, for consistency, it is valid and has an obvious interpretation and the alpha is that of the origin color

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Received on Wednesday, 20 August 2025 09:02:43 UTC