module CSS makes postcode form element invisible on Olivero

Problem/Motivation

On Olivero, Drupal's default theme, the postcode form element is invisible because of this CSS rule:

> border: 0.125rem solid var(--color-black);

My browser tells me this is because (--color-black) is not set.

I'd say that this sort of cosmetic change isn't something the module should be doing, rather it's up to the site theme.

(The 'text-transform: uppercase;' is a nice touch though!)

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes