#426EA5

CSS

:root {
  --song-of-the-sea: #426ea5;
  --song-of-the-sea-rgb: 66 110 165;
  --song-of-the-sea-oklch: oklch(0.532 0.1 254.8);
}

.element {
  color: var(--song-of-the-sea);
  background-color: hsl(213 43% 45%);
  border-color: oklch(0.532 0.1 254.8);
}

Tailwind CSS v4

@theme {
  --color-song-of-the-sea: #426ea5;
  --color-song-of-the-sea-50: #e3f7ff;
  --color-song-of-the-sea-100: #d3eaff;
  --color-song-of-the-sea-200: #b9d7ff;
  --color-song-of-the-sea-300: #97baeb;
  --color-song-of-the-sea-400: #75a1d9;
  --color-song-of-the-sea-500: #5688c7;
  --color-song-of-the-sea-600: #4a73a8;
  --color-song-of-the-sea-700: #3b5c87;
  --color-song-of-the-sea-800: #284464;
  --color-song-of-the-sea-900: #1b2f46;
  --color-song-of-the-sea-950: #0b1b2e;
}

SCSS

$song-of-the-sea: #426ea5;
$song-of-the-sea-rgb: 66, 110, 165;
$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);
}