#3B709C

CSS

:root {
  --muted-blue: #3b709c;
  --muted-blue-rgb: 59 112 156;
  --muted-blue-oklch: oklch(0.528 0.09 245.7);
}

.element {
  color: var(--muted-blue);
  background-color: hsl(207 45% 42%);
  border-color: oklch(0.528 0.09 245.7);
}

Tailwind CSS v4

@theme {
  --color-muted-blue: #3b709c;
  --color-muted-blue-50: #e2f8ff;
  --color-muted-blue-100: #d1ebff;
  --color-muted-blue-200: #b7d8f9;
  --color-muted-blue-300: #93bce4;
  --color-muted-blue-400: #71a4d1;
  --color-muted-blue-500: #508cbe;
  --color-muted-blue-600: #4476a0;
  --color-muted-blue-700: #365f81;
  --color-muted-blue-800: #25465f;
  --color-muted-blue-900: #193043;
  --color-muted-blue-950: #091c2b;
}

SCSS

$muted-blue: #3b709c;
$muted-blue-rgb: 59, 112, 156;
$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);
}