[csswg-drafts] Pull Request: [css-color-4] consistently name color-mod()

jonathantneal has just submitted a new pull request for https://github.com/w3c/csswg-drafts:

== [css-color-4] consistently name color-mod() ==
Uses the `color-mod()` function name consistently in order to avoid confusion with the `color()` function.

See https://github.com/w3c/csswg-drafts/pull/2196