Retail palettes with exactly one CTA-grade tone, so "add to cart" never competes with a sale badge. Neutrals stay quiet to let product photography be the loudest thing on the page.
Mint owns the primary action and nothing else, so "confirm" is unmistakable. Neutrals stay warm-grey to keep the app friendly, not clinical.
Gold is a metal, not a highlighter — it works at 8% of the surface area, sitting on true blacks with a warm cast.