#1B4655

CSS

:root {
  --cold-and-dark: #1b4655;
  --cold-and-dark-rgb: 27 70 85;
  --cold-and-dark-oklch: oklch(0.371 0.054 224.1);
}

.element {
  color: var(--cold-and-dark);
  background-color: hsl(196 52% 22%);
  border-color: oklch(0.371 0.054 224.1);
}

Tailwind CSS v4

@theme {
  --color-cold-and-dark: #1b4655;
  --color-cold-and-dark-50: #e6f9ff;
  --color-cold-and-dark-100: #d6ecf6;
  --color-cold-and-dark-200: #bddae6;
  --color-cold-and-dark-300: #9bbecd;
  --color-cold-and-dark-400: #7ca6b6;
  --color-cold-and-dark-500: #5e8ea1;
  --color-cold-and-dark-600: #507888;
  --color-cold-and-dark-700: #40606d;
  --color-cold-and-dark-800: #2d4750;
  --color-cold-and-dark-900: #1e3138;
  --color-cold-and-dark-950: #0e1d22;
}

SCSS

$cold-and-dark: #1b4655;
$cold-and-dark-rgb: 27, 70, 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);
}