Description

Recent updates to the SASS dependency (see #1597 and #1594) have started to display deprecation notices durung the grunt sass:colors build step.

This PR aims to address these notices by modernising and updating the scss files, rather than simply silence the warnings.

Motivation and context

Cleaner build output.

How has this been tested?

Local testing and comparison of built files.

To compare before and after, on develop run grunt sass:colors and note the deprecation notices. Repeat that on this PR and see clean output.

To compare the built CSS before and after, use the following series of commands to build the current CSS, rename the folder in build/, build the CSS from the new file and then compare them. The final command should report nothing:

git checkout develop 
grunt sass:colors
mv build/wp-admin/css/colors build/wp-admin/css/current-colors/
git checkout update/modernise-scss
grunt sass:colors
diff -ur build/wp-admin/css/colors build/wp-admin/css/current-colors/

Screenshots

Before

After

Types of changes

• Bug fix

Can confirm that there are no more deprecations and diff return no changes.

Shared this upstream at WordPress:
https://core.trac.wordpress.org/ticket/62323