Blue-Black

CSS

:root {
  --blue-black: #24313d;
  --blue-black-rgb: 36 49 61;
  --blue-black-oklch: oklch(0.307 0.028 246.7);
}

.element {
  color: var(--blue-black);
  background-color: hsl(209 26% 19%);
  border-color: oklch(0.307 0.028 246.7);
}

Tailwind CSS v4

@theme {
  --color-blue-black: #24313d;
  --color-blue-black-50: #eff6fd;
  --color-blue-black-100: #e1e9f1;
  --color-blue-black-200: #cbd6e0;
  --color-blue-black-300: #adb9c5;
  --color-blue-black-400: #92a0ae;
  --color-blue-black-500: #788898;
  --color-blue-black-600: #657381;
  --color-blue-black-700: #515c67;
  --color-blue-black-800: #3a444c;
  --color-blue-black-900: #282f34;
  --color-blue-black-950: #161b20;
}

SCSS

$blue-black: #24313d;
$blue-black-rgb: 36, 49, 61;
$blue-black-light: mix(#fff, $blue-black, 20%);
$blue-black-dark: mix(#000, $blue-black, 20%);

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