#2F71A4

CSS

:root {
  --muted-blue: #2f71a4;
  --muted-blue-rgb: 47 113 164;
  --muted-blue-oklch: oklch(0.53 0.104 245.1);
}

.element {
  color: var(--muted-blue);
  background-color: hsl(206 55% 41%);
  border-color: oklch(0.53 0.104 245.1);
}

Tailwind CSS v4

@theme {
  --color-muted-blue: #2f71a4;
  --color-muted-blue-50: #def9ff;
  --color-muted-blue-100: #cdecff;
  --color-muted-blue-200: #b1d9ff;
  --color-muted-blue-300: #8cbdea;
  --color-muted-blue-400: #67a5d8;
  --color-muted-blue-500: #438cc7;
  --color-muted-blue-600: #3a77a8;
  --color-muted-blue-700: #2e5f87;
  --color-muted-blue-800: #1e4664;
  --color-muted-blue-900: #143146;
  --color-muted-blue-950: #051d2d;
}

SCSS

$muted-blue: #2f71a4;
$muted-blue-rgb: 47, 113, 164;
$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);
}