#003C4B

CSS

:root {
  --cold-and-dark: #003c4b;
  --cold-and-dark-rgb: 0 60 75;
  --cold-and-dark-oklch: oklch(0.33 0.06 220.9);
}

.element {
  color: var(--cold-and-dark);
  background-color: hsl(192 100% 15%);
  border-color: oklch(0.33 0.06 220.9);
}

Tailwind CSS v4

@theme {
  --color-cold-and-dark: #003c4b;
  --color-cold-and-dark-50: #e4f9ff;
  --color-cold-and-dark-100: #d3edf7;
  --color-cold-and-dark-200: #b9dbe7;
  --color-cold-and-dark-300: #96bfce;
  --color-cold-and-dark-400: #76a7b8;
  --color-cold-and-dark-500: #5690a2;
  --color-cold-and-dark-600: #4a7a89;
  --color-cold-and-dark-700: #3b616e;
  --color-cold-and-dark-800: #294851;
  --color-cold-and-dark-900: #1c3238;
  --color-cold-and-dark-950: #0c1d23;
}

SCSS

$cold-and-dark: #003c4b;
$cold-and-dark-rgb: 0, 60, 75;
$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);
}