Pink button/link style in Umami fails WCAG 2.0 SC 1.4.3 Contrast (minimum)

Problem/Motivation

The link field in the Banner Block is white text on a pink background. This combination has a colour contrast ratio of 3.9:1.

The contrast ratio of 3.9:1 satisfies minimum contrast for WCAG 2.0 level AA, but note that it's in the special exception range for large-scale text. The link text is normal weight, and has a computed size of 19.2 CSS pixels. This doesn't meet the requirements for large-scale text, so this is a WCAG 2.0 failure.

This might be down to a confusion between points vs pixels. See this note from Understanding SC 1.4.3 Contrast (Minimum):

Note 1: When evaluating this success criterion, the font size in points should be obtained from the user agent or calculated on font metrics in the way that user agents do. Point sizes are based on the CSS pt size as defined in CSS3 Values. The ratio between sizes in points and CSS pixels is 1pt = 1.333px, therefore 14pt and 18pt are equivalent to approximately 18.5px and 24px.

Proposed resolution

Possible solutions, any of these will satisfy WCAG 2.0 SC 1.4.3 Contrast (minimum) for level AA conformance:

• Use #D93760 which was already on an old style guide (comment #9), and has ration 4.5:1 with white. PREFERRED: increase the colour contrast to 4.5:1, using a deeper shade of pink. Currently we are already at 3.9:1, so we might achieve 4.5:1 without drastically changing the the present colour palette. This approach is preferred because it's more flexible and re-usable; it passes without worrying about text size.
• Increase the font weight to 700 (bold), and confirm that all instances of this bg/fg colour combination have a computed size of at least 18.5 CSS pixels.
• Increase the font-size, to a computed size of at least 24 CSS pixels, and confirm that all instances of this bg/fg colour combination have a computed size of at least 24 CSS pixels.

Remaining tasks

Explore styles, especially a deeper pink which gets us to 4.5:1 contrast. Screenshots / mockups useful. Tip: treat the pink as a HSV color, and only adjust the -V part.
Patch.
Screenshots will be a useful confirmation, e.g. including evidence of computed font size form dev tools.

User interface changes

A small design change is required, whichever solution we use.

API changes

None.

Data model changes

None.