#335573

CSS

:root {
  --dark-blue: #335573;
  --dark-blue-rgb: 51 85 115;
  --dark-blue-oklch: oklch(0.437 0.064 246.5);
}

.element {
  color: var(--dark-blue);
  background-color: hsl(208 39% 33%);
  border-color: oklch(0.437 0.064 246.5);
}

Tailwind CSS v4

@theme {
  --color-dark-blue: #335573;
  --color-dark-blue-50: #e8f7ff;
  --color-dark-blue-100: #d8eafd;
  --color-dark-blue-200: #c0d7ef;
  --color-dark-blue-300: #9fbbd7;
  --color-dark-blue-400: #80a3c2;
  --color-dark-blue-500: #638bae;
  --color-dark-blue-600: #547593;
  --color-dark-blue-700: #435e76;
  --color-dark-blue-800: #2f4557;
  --color-dark-blue-900: #20303d;
  --color-dark-blue-950: #0f1c26;
}

SCSS

$dark-blue: #335573;
$dark-blue-rgb: 51, 85, 115;
$dark-blue-light: mix(#fff, $dark-blue, 20%);
$dark-blue-dark: mix(#000, $dark-blue, 20%);

.element {
  color: $dark-blue;
  box-shadow: 0 0 0 2px rgba($dark-blue, 0.35);
}