Post Template: Applying background color adds inconsistent padding in the Editor

[ndiego]

Description

If you add background color to the Post Template block, it inherits padding from the styles from the List block in the Editor:

ol.has-background,ul.has-background {
    padding: 1.25em 2.375em
}

This padding is not applied on the front end, which is correct, in my opinion. We need to remove the padding in the Editor.

This issue seems related to #59455, cc @tellthemachines @ramonjd

Step-by-step reproduction instructions

1. Open a new Playground instance and navigate to the Post Editor
2. Using a Pattern, add one of the Posts options
3. Inside the Post Template block, wrap all internal blocks in a Group and see the background color on the Group to any color.
4. Then set the background color on the Post Template block to a different color. Notice how the padding is applied and that it does not show up on the frontend.

Screenshots, screen recording, code snippet

Editor	Frontend

Environment info

• WordPress 6.5.3
• Gutenberg 18.3

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes

[ramonjd]

I think this may have been fixed by:

• Styles: try wrapping with :root to fix reset styles #61638

Which reduces the specificity of the rule:

:root :where(ul.has-background,ol.has-background) {
    padding: 1.25em 2.375em;
}

Given the above rule, the padding on the ul.wp-block-post-template in the editor is being reset here:

gutenberg/packages/block-library/src/post-template/style.scss

Line 6 in faf5cba

padding: 0;