#3F6CB3

CSS

:root {
  --song-of-the-sea: #3f6cb3;
  --song-of-the-sea-rgb: 63 108 179;
  --song-of-the-sea-oklch: oklch(0.534 0.123 259.2);
}

.element {
  color: var(--song-of-the-sea);
  background-color: hsl(217 48% 47%);
  border-color: oklch(0.534 0.123 259.2);
}

Tailwind CSS v4

@theme {
  --color-song-of-the-sea: #3f6cb3;
  --color-song-of-the-sea-50: #e2f6ff;
  --color-song-of-the-sea-100: #d1e9ff;
  --color-song-of-the-sea-200: #b7d5ff;
  --color-song-of-the-sea-300: #94b8f7;
  --color-song-of-the-sea-400: #729fe6;
  --color-song-of-the-sea-500: #5285d6;
  --color-song-of-the-sea-600: #4671b5;
  --color-song-of-the-sea-700: #385b91;
  --color-song-of-the-sea-800: #25436c;
  --color-song-of-the-sea-900: #192e4c;
  --color-song-of-the-sea-950: #091a32;
}

SCSS

$song-of-the-sea: #3f6cb3;
$song-of-the-sea-rgb: 63, 108, 179;
$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);
}