#356FA8

CSS

:root {
  --muted-blue: #356fa8;
  --muted-blue-rgb: 53 111 168;
  --muted-blue-oklch: oklch(0.53 0.109 250.3);
}

.element {
  color: var(--muted-blue);
  background-color: hsl(210 52% 43%);
  border-color: oklch(0.53 0.109 250.3);
}

Tailwind CSS v4

@theme {
  --color-muted-blue: #356fa8;
  --color-muted-blue-50: #e0f8ff;
  --color-muted-blue-100: #cfebff;
  --color-muted-blue-200: #b3d8ff;
  --color-muted-blue-300: #8fbbee;
  --color-muted-blue-400: #6ba3dc;
  --color-muted-blue-500: #498acb;
  --color-muted-blue-600: #3f75ab;
  --color-muted-blue-700: #325e8a;
  --color-muted-blue-800: #214566;
  --color-muted-blue-900: #163048;
  --color-muted-blue-950: #071c2f;
}

SCSS

$muted-blue: #356fa8;
$muted-blue-rgb: 53, 111, 168;
$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);
}