#5173B9

CSS

:root {
  --song-of-the-sea: #5173b9;
  --song-of-the-sea-rgb: 81 115 185;
  --song-of-the-sea-oklch: oklch(0.562 0.116 263.5);
}

.element {
  color: var(--song-of-the-sea);
  background-color: hsl(220 43% 52%);
  border-color: oklch(0.562 0.116 263.5);
}

Tailwind CSS v4

@theme {
  --color-song-of-the-sea: #5173b9;
  --color-song-of-the-sea-50: #e5f5ff;
  --color-song-of-the-sea-100: #d5e8ff;
  --color-song-of-the-sea-200: #bdd4ff;
  --color-song-of-the-sea-300: #9bb7f4;
  --color-song-of-the-sea-400: #7b9de3;
  --color-song-of-the-sea-500: #5d84d3;
  --color-song-of-the-sea-600: #4f70b2;
  --color-song-of-the-sea-700: #3f598f;
  --color-song-of-the-sea-800: #2b426a;
  --color-song-of-the-sea-900: #1d2d4b;
  --color-song-of-the-sea-950: #0d1a31;
}

SCSS

$song-of-the-sea: #5173b9;
$song-of-the-sea-rgb: 81, 115, 185;
$song-of-the-sea-light: mix(#fff, $song-of-the-sea, 20%);
$song-of-the-sea-dark: mix(#000, $song-of-the-sea, 20%);

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