Color contrast: have skip links use a black color rather than navy

[srietkerk]

Fixes microsoft/pxt-microbit#6198

[Copilot]

Pull Request Overview

This PR addresses color contrast by updating skip links to use a black color rather than the previous navy shade. Key changes include:

• Updating the skip link color in style.css from #387894 to black.
• Replacing the hex color in accessibility.less with the CSS variable var(--pxt-neutral-foreground1).

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
theme/accessibility.less	Updated accessible menu color to use a CSS variable
docfiles/style.css	Explicitly set skip link color to black as required for better contrast

Comments suppressed due to low confidence (1)

theme/accessibility.less:14

• Ensure that the CSS variable '--pxt-neutral-foreground1' resolves exactly to black for skip links, as the PR title indicates a requirement for black color contrast.

@accessibleMenuColor: var(--pxt-neutral-foreground1);

[thsparks]

Since the background is hard-coded, we should probably hard-code the foreground to black as well. (Otherwise, it'll probably be white on white in dark mode).

In an ideal world, we'd have both be theme colors instead of hard-coded, but I think a white fade makes sense here regardless of theme, so I guess it's fine. Otherwise we'd have to add theme vars for that 90% white color, which I don't think we really have at the moment (kind of the inverse of the neutral-alpha colors)...I wouldn't worry about it for now unless we find ourselves using this white fade in more places.

[thsparks]

To clarify, this is a long-winded way of me saying that this is a rare case where we should probably just hard-code the foreground to black so it's guaranteed to contrast with the hard-coded white fade.