Twenty Fifteen: Button blocks don't apply custom colours

[laurelfulford]

The selectors used for Twenty Fifteen's button blocks are too specific, the styles for the editor custom colours don't override them on the front-end.

[laurelfulford]

Twenty Fifteen - custom colours applied in editor

[laurelfulford]

Twenty Fifteen - custom colours on front end, before

[laurelfulford]

Twenty Fifteen - custom colours on front end, after

[laurelfulford]

45428.patch​ moves the colour and background colours on the button to a slightly less specific selector, so the custom colours can override them.

[davidakennedy]

Hi @laurelfulford! I tested this one, and it's good to go.

[Joen]

Patch looks good 👍 👍! 🚀

[laurelfulford]

In 44198:

Twenty Fifteen: Fix button block custom colors on front end.

Simplify some of the button block’s CSS selectors in the theme, to make sure the default colors don’t override the custom colors on the front end.

Fixes #45428.

[desrosj]

Reopening and marking fixed-5.0 so that this can be properly merged into trunk.

[desrosj]

In 44306:

Bundled Themes: Fix button block custom colors on front end.

Simplify some of the button block’s CSS selectors in the theme, to make sure the default colors don’t override the custom colors on the front end.

This fix is applied to Twenty Sixteen, Twenty Fifteen and Twenty Fourteen.

Props laurelfulford.

Merges [44197-44198] and [44200] into trunk.

Fixes #45428, #45429.