#647B5E

CSS

:root {
  --emerald-city: #647b5e;
  --emerald-city-rgb: 100 123 94;
  --emerald-city-oklch: oklch(0.556 0.051 139.2);
}

.element {
  color: var(--emerald-city);
  background-color: hsl(108 13% 43%);
  border-color: oklch(0.556 0.051 139.2);
}

Tailwind CSS v4

@theme {
  --color-emerald-city: #647b5e;
  --color-emerald-city-50: #edf9eb;
  --color-emerald-city-100: #dfeddd;
  --color-emerald-city-200: #c9dac6;
  --color-emerald-city-300: #a9bea6;
  --color-emerald-city-400: #8fa689;
  --color-emerald-city-500: #758f6e;
  --color-emerald-city-600: #63795d;
  --color-emerald-city-700: #4f614a;
  --color-emerald-city-800: #3a4735;
  --color-emerald-city-900: #283124;
  --color-emerald-city-950: #161d13;
}

SCSS

$emerald-city: #647b5e;
$emerald-city-rgb: 100, 123, 94;
$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);
}