#004050

CSS

:root {
  --cold-and-dark: #004050;
  --cold-and-dark-rgb: 0 64 80;
  --cold-and-dark-oklch: oklch(0.344 0.063 221.2);
}

.element {
  color: var(--cold-and-dark);
  background-color: hsl(192 100% 16%);
  border-color: oklch(0.344 0.063 221.2);
}

Tailwind CSS v4

@theme {
  --color-cold-and-dark: #004050;
  --color-cold-and-dark-50: #e3faff;
  --color-cold-and-dark-100: #d2edf8;
  --color-cold-and-dark-200: #b8dbe8;
  --color-cold-and-dark-300: #95bfcf;
  --color-cold-and-dark-400: #74a7b9;
  --color-cold-and-dark-500: #5490a4;
  --color-cold-and-dark-600: #477a8a;
  --color-cold-and-dark-700: #39626f;
  --color-cold-and-dark-800: #284851;
  --color-cold-and-dark-900: #1b3239;
  --color-cold-and-dark-950: #0b1e23;
}

SCSS

$cold-and-dark: #004050;
$cold-and-dark-rgb: 0, 64, 80;
$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);
}