#2B71A3

CSS

:root {
  --muted-blue: #2b71a3;
  --muted-blue-rgb: 43 113 163;
  --muted-blue-oklch: oklch(0.528 0.105 243.5);
}

.element {
  color: var(--muted-blue);
  background-color: hsl(205 58% 40%);
  border-color: oklch(0.528 0.105 243.5);
}

Tailwind CSS v4

@theme {
  --color-muted-blue: #2b71a3;
  --color-muted-blue-50: #ddf9ff;
  --color-muted-blue-100: #ccecff;
  --color-muted-blue-200: #b0daff;
  --color-muted-blue-300: #8abdea;
  --color-muted-blue-400: #65a5d8;
  --color-muted-blue-500: #3f8dc6;
  --color-muted-blue-600: #3777a7;
  --color-muted-blue-700: #2c6086;
  --color-muted-blue-800: #1c4663;
  --color-muted-blue-900: #123146;
  --color-muted-blue-950: #041d2d;
}

SCSS

$muted-blue: #2b71a3;
$muted-blue-rgb: 43, 113, 163;
$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);
}