Accessibility: Some elements don't meet color contrast ratio requirements

[bedmison]

This manifests everywhere that the current theme is being used. The teal labels on the beige backgrounds don't have the necessary contrast.

Additionally, it also shows up in the Code-Mirror theme used.

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From the WCAG 2.1 spec:

Ensure all text elements have sufficient color contrast between the text in the foreground and background color behind it.

Success Criterion: Ensure color contrast of at least 4.5:1 for small text or 3:1 for large text, even if text is part of an image. Large text has been defined in the requirements as 18pt (24 CSS pixels) or 14pt bold (19 CSS pixels). Note: Elements found to have a 1:1 ratio are considered "incomplete" and require a manual review.