Accent color
The one loud color you spend sparingly: buttons, links, the thing you want clicked. Everything else stays quiet so it lands.
See it
What it is
The high-attention color you reserve for a tiny slice of the screen: primary buttons, links, active states, the one number on the dashboard that matters. It works by scarcity. Against a field of neutrals, a single saturated color reads as 'look here' before anyone has parsed a word.
Pick it last, after the neutrals are settled, and pick for separation rather than beauty: the accent should be far from your surfaces in both hue and lightness. Then ration it. If the accent covers a third of the page it is just another background, and the actual buttons have nothing left to stand out against.
Gotcha: your brand color is not automatically your accent color. Many brand hues (mid-tone blues, bright greens, most yellows) fail contrast the moment you put white label text on them, so the interface accent usually ends up a darker or more chromatic cousin of the brand color. Also keep the accent away from the semantic reds and greens, or people will read 'delete' where you meant 'continue'.
Ask AI for it
Pick a single accent color for this interface. Keep every surface, border and body text neutral, and use the accent only on primary buttons, links, focus rings and active nav states (target under 10% of the pixels). The accent must hit at least 4.5:1 against the page background and against white label text, and must not be red or green so it stays distinct from the status colors. Give me the hex, a hover shade, and a 12%-opacity tint for subtle backgrounds.