#315A63

CSS

:root {
  --arctic-nights: #315a63;
  --arctic-nights-rgb: 49 90 99;
  --arctic-nights-oklch: oklch(0.441 0.048 213.4);
}

.element {
  color: var(--arctic-nights);
  background-color: hsl(191 34% 29%);
  border-color: oklch(0.441 0.048 213.4);
}

Tailwind CSS v4

@theme {
  --color-arctic-nights: #315a63;
  --color-arctic-nights-50: #e7f9fe;
  --color-arctic-nights-100: #d7ecf2;
  --color-arctic-nights-200: #bedae1;
  --color-arctic-nights-300: #9cbec7;
  --color-arctic-nights-400: #7ea6b0;
  --color-arctic-nights-500: #608f9a;
  --color-arctic-nights-600: #527982;
  --color-arctic-nights-700: #416168;
  --color-arctic-nights-800: #2e474c;
  --color-arctic-nights-900: #1f3135;
  --color-arctic-nights-950: #0f1d20;
}

SCSS

$arctic-nights: #315a63;
$arctic-nights-rgb: 49, 90, 99;
$arctic-nights-light: mix(#fff, $arctic-nights, 20%);
$arctic-nights-dark: mix(#000, $arctic-nights, 20%);

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