#456EA1

CSS

:root {
  --song-of-the-sea: #456ea1;
  --song-of-the-sea-rgb: 69 110 161;
  --song-of-the-sea-oklch: oklch(0.531 0.093 254.6);
}

.element {
  color: var(--song-of-the-sea);
  background-color: hsl(213 40% 45%);
  border-color: oklch(0.531 0.093 254.6);
}

Tailwind CSS v4

@theme {
  --color-song-of-the-sea: #456ea1;
  --color-song-of-the-sea-50: #e4f7ff;
  --color-song-of-the-sea-100: #d4eaff;
  --color-song-of-the-sea-200: #bbd6fc;
  --color-song-of-the-sea-300: #99bae7;
  --color-song-of-the-sea-400: #78a1d5;
  --color-song-of-the-sea-500: #5a89c3;
  --color-song-of-the-sea-600: #4d74a4;
  --color-song-of-the-sea-700: #3d5c84;
  --color-song-of-the-sea-800: #2a4462;
  --color-song-of-the-sea-900: #1c2f45;
  --color-song-of-the-sea-950: #0c1b2c;
}

SCSS

$song-of-the-sea: #456ea1;
$song-of-the-sea-rgb: 69, 110, 161;
$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);
}