#3870A1

CSS

:root {
  --muted-blue: #3870a1;
  --muted-blue-rgb: 56 112 161;
  --muted-blue-oklch: oklch(0.53 0.098 247.3);
}

.element {
  color: var(--muted-blue);
  background-color: hsl(208 48% 43%);
  border-color: oklch(0.53 0.098 247.3);
}

Tailwind CSS v4

@theme {
  --color-muted-blue: #3870a1;
  --color-muted-blue-50: #e1f8ff;
  --color-muted-blue-100: #d0ebff;
  --color-muted-blue-200: #b5d8fd;
  --color-muted-blue-300: #91bce8;
  --color-muted-blue-400: #6ea4d5;
  --color-muted-blue-500: #4c8bc3;
  --color-muted-blue-600: #4176a5;
  --color-muted-blue-700: #345e84;
  --color-muted-blue-800: #234662;
  --color-muted-blue-900: #173045;
  --color-muted-blue-950: #081c2c;
}

SCSS

$muted-blue: #3870a1;
$muted-blue-rgb: 56, 112, 161;
$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);
}