#3F709A

CSS

:root {
  --muted-blue: #3f709a;
  --muted-blue-rgb: 63 112 154;
  --muted-blue-oklch: oklch(0.529 0.085 246.2);
}

.element {
  color: var(--muted-blue);
  background-color: hsl(208 42% 43%);
  border-color: oklch(0.529 0.085 246.2);
}

Tailwind CSS v4

@theme {
  --color-muted-blue: #3f709a;
  --color-muted-blue-50: #e3f8ff;
  --color-muted-blue-100: #d2ebff;
  --color-muted-blue-200: #b8d8f8;
  --color-muted-blue-300: #95bce2;
  --color-muted-blue-400: #74a4ce;
  --color-muted-blue-500: #548bbb;
  --color-muted-blue-600: #48769e;
  --color-muted-blue-700: #395e7f;
  --color-muted-blue-800: #27455e;
  --color-muted-blue-900: #1a3042;
  --color-muted-blue-950: #0a1c2a;
}

SCSS

$muted-blue: #3f709a;
$muted-blue-rgb: 63, 112, 154;
$muted-blue-light: mix(#fff, $muted-blue, 20%);
$muted-blue-dark: mix(#000, $muted-blue, 20%);

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