#637B62

CSS

:root {
  --emerald-city: #637b62;
  --emerald-city-rgb: 99 123 98;
  --emerald-city-oklch: oklch(0.556 0.047 143.9);
}

.element {
  color: var(--emerald-city);
  background-color: hsl(118 11% 43%);
  border-color: oklch(0.556 0.047 143.9);
}

Tailwind CSS v4

@theme {
  --color-emerald-city: #637b62;
  --color-emerald-city-50: #edf9ed;
  --color-emerald-city-100: #deecdf;
  --color-emerald-city-200: #c8dac8;
  --color-emerald-city-300: #a9bea9;
  --color-emerald-city-400: #8ea68d;
  --color-emerald-city-500: #748f72;
  --color-emerald-city-600: #627961;
  --color-emerald-city-700: #4e614d;
  --color-emerald-city-800: #394738;
  --color-emerald-city-900: #273126;
  --color-emerald-city-950: #151d14;
}

SCSS

$emerald-city: #637b62;
$emerald-city-rgb: 99, 123, 98;
$emerald-city-light: mix(#fff, $emerald-city, 20%);
$emerald-city-dark: mix(#000, $emerald-city, 20%);

.element {
  color: $emerald-city;
  box-shadow: 0 0 0 2px rgba($emerald-city, 0.35);
}