#03060F

CSS

:root {
  --dark-rift: #03060f;
  --dark-rift-rgb: 3 6 15;
  --dark-rift-oklch: oklch(0.123 0.023 263);
}

.element {
  color: var(--dark-rift);
  background-color: hsl(225 67% 4%);
  border-color: oklch(0.123 0.023 263);
}

Tailwind CSS v4

@theme {
  --color-dark-rift: #03060f;
  --color-dark-rift-50: #f2f5fc;
  --color-dark-rift-100: #e4e8f0;
  --color-dark-rift-200: #cfd4df;
  --color-dark-rift-300: #b1b7c4;
  --color-dark-rift-400: #979fad;
  --color-dark-rift-500: #7e8696;
  --color-dark-rift-600: #6b727f;
  --color-dark-rift-700: #555b66;
  --color-dark-rift-800: #3e434b;
  --color-dark-rift-900: #2a2e34;
  --color-dark-rift-950: #181b1f;
}

SCSS

$dark-rift: #03060f;
$dark-rift-rgb: 3, 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);
}