The aurora-development skill explains how the brand and accent colours
chosen under Settings › Website › Branding reach blocks: the brand-palette
partial's --color-brand-* and --color-accent-* shades, defined as the
site's defaults in plain @theme (not inline), blocks painted with
brand-* and accent-* rather than fixed colours, contrast between shades,
and Fields::tone() turned into whole class names. The porting guide maps
an old site's colours onto them, and the guideline says so.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>