#00664A

CSS

:root {
  --into-the-green: #00664a;
  --into-the-green-rgb: 0 102 74;
  --into-the-green-oklch: oklch(0.453 0.094 166.2);
}

.element {
  color: var(--into-the-green);
  background-color: hsl(164 100% 20%);
  border-color: oklch(0.453 0.094 166.2);
}

Tailwind CSS v4

@theme {
  --color-into-the-green: #00664a;
  --color-into-the-green-50: #dcfef0;
  --color-into-the-green-100: #cbf3e2;
  --color-into-the-green-200: #aee2cd;
  --color-into-the-green-300: #87c7ae;
  --color-into-the-green-400: #64b092;
  --color-into-the-green-500: #3c9a78;
  --color-into-the-green-600: #348266;
  --color-into-the-green-700: #2a6851;
  --color-into-the-green-800: #1e4d3a;
  --color-into-the-green-900: #143528;
  --color-into-the-green-950: #052016;
}

SCSS

$into-the-green: #00664a;
$into-the-green-rgb: 0, 102, 74;
$into-the-green-light: mix(#fff, $into-the-green, 20%);
$into-the-green-dark: mix(#000, $into-the-green, 20%);

.element {
  color: $into-the-green;
  box-shadow: 0 0 0 2px rgba($into-the-green, 0.35);
}