#5174B4

CSS

:root {
  --song-of-the-sea: #5174b4;
  --song-of-the-sea-rgb: 81 116 180;
  --song-of-the-sea-oklch: oklch(0.562 0.108 261.7);
}

.element {
  color: var(--song-of-the-sea);
  background-color: hsl(219 40% 51%);
  border-color: oklch(0.562 0.108 261.7);
}

Tailwind CSS v4

@theme {
  --color-song-of-the-sea: #5174b4;
  --color-song-of-the-sea-50: #e6f6ff;
  --color-song-of-the-sea-100: #d6e8ff;
  --color-song-of-the-sea-200: #bdd5ff;
  --color-song-of-the-sea-300: #9bb7ef;
  --color-song-of-the-sea-400: #7b9ede;
  --color-song-of-the-sea-500: #5e85cd;
  --color-song-of-the-sea-600: #5071ad;
  --color-song-of-the-sea-700: #3f5a8b;
  --color-song-of-the-sea-800: #2c4267;
  --color-song-of-the-sea-900: #1d2e49;
  --color-song-of-the-sea-950: #0d1a30;
}

SCSS

$song-of-the-sea: #5174b4;
$song-of-the-sea-rgb: 81, 116, 180;
$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);
}