#5076B9

CSS

:root {
  --endless-river: #5076b9;
  --endless-river-rgb: 80 118 185;
  --endless-river-oklch: oklch(0.568 0.113 261.1);
}

.element {
  color: var(--endless-river);
  background-color: hsl(218 43% 52%);
  border-color: oklch(0.568 0.113 261.1);
}

Tailwind CSS v4

@theme {
  --color-endless-river: #5076b9;
  --color-endless-river-50: #e4f6ff;
  --color-endless-river-100: #d4e9ff;
  --color-endless-river-200: #bbd5ff;
  --color-endless-river-300: #99b8f2;
  --color-endless-river-400: #789fe1;
  --color-endless-river-500: #5a85d0;
  --color-endless-river-600: #4d71b0;
  --color-endless-river-700: #3d5a8d;
  --color-endless-river-800: #2a4269;
  --color-endless-river-900: #1c2e4a;
  --color-endless-river-950: #0c1a31;
}

SCSS

$endless-river: #5076b9;
$endless-river-rgb: 80, 118, 185;
$endless-river-light: mix(#fff, $endless-river, 20%);
$endless-river-dark: mix(#000, $endless-river, 20%);

.element {
  color: $endless-river;
  box-shadow: 0 0 0 2px rgba($endless-river, 0.35);
}