#00060F

CSS

:root {
  --dark-rift: #00060f;
  --dark-rift-rgb: 0 6 15;
  --dark-rift-oklch: oklch(0.118 0.029 243.8);
}

.element {
  color: var(--dark-rift);
  background-color: hsl(216 100% 3%);
  border-color: oklch(0.118 0.029 243.8);
}

Tailwind CSS v4

@theme {
  --color-dark-rift: #00060f;
  --color-dark-rift-50: #eff6fd;
  --color-dark-rift-100: #e0e9f1;
  --color-dark-rift-200: #cbd6e0;
  --color-dark-rift-300: #acb9c6;
  --color-dark-rift-400: #91a1af;
  --color-dark-rift-500: #768998;
  --color-dark-rift-600: #647481;
  --color-dark-rift-700: #505d67;
  --color-dark-rift-800: #3a444c;
  --color-dark-rift-900: #282f35;
  --color-dark-rift-950: #161b20;
}

SCSS

$dark-rift: #00060f;
$dark-rift-rgb: 0, 6, 15;
$dark-rift-light: mix(#fff, $dark-rift, 20%);
$dark-rift-dark: mix(#000, $dark-rift, 20%);

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