#004555

CSS

:root {
  --cold-and-dark: #004555;
  --cold-and-dark-rgb: 0 69 85;
  --cold-and-dark-oklch: oklch(0.361 0.066 219.8);
}

.element {
  color: var(--cold-and-dark);
  background-color: hsl(191 100% 17%);
  border-color: oklch(0.361 0.066 219.8);
}

Tailwind CSS v4

@theme {
  --color-cold-and-dark: #004555;
  --color-cold-and-dark-50: #e2faff;
  --color-cold-and-dark-100: #d1edf8;
  --color-cold-and-dark-200: #b7dbe8;
  --color-cold-and-dark-300: #93c0d0;
  --color-cold-and-dark-400: #72a8b9;
  --color-cold-and-dark-500: #5091a4;
  --color-cold-and-dark-600: #457a8b;
  --color-cold-and-dark-700: #37626f;
  --color-cold-and-dark-800: #264851;
  --color-cold-and-dark-900: #193239;
  --color-cold-and-dark-950: #0a1e23;
}

SCSS

$cold-and-dark: #004555;
$cold-and-dark-rgb: 0, 69, 85;
$cold-and-dark-light: mix(#fff, $cold-and-dark, 20%);
$cold-and-dark-dark: mix(#000, $cold-and-dark, 20%);

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