#00202B

CSS

:root {
  --black-box: #00202b;
  --black-box-rgb: 0 32 43;
  --black-box-oklch: oklch(0.226 0.043 224.8);
}

.element {
  color: var(--black-box);
  background-color: hsl(195 100% 8%);
  border-color: oklch(0.226 0.043 224.8);
}

Tailwind CSS v4

@theme {
  --color-black-box: #00202b;
  --color-black-box-50: #e9f8ff;
  --color-black-box-100: #daebf3;
  --color-black-box-200: #c2d8e3;
  --color-black-box-300: #a1bcc9;
  --color-black-box-400: #84a4b2;
  --color-black-box-500: #678d9c;
  --color-black-box-600: #587784;
  --color-black-box-700: #465f69;
  --color-black-box-800: #32464d;
  --color-black-box-900: #223036;
  --color-black-box-950: #111d21;
}

SCSS

$black-box: #00202b;
$black-box-rgb: 0, 32, 43;
$black-box-light: mix(#fff, $black-box, 20%);
$black-box-dark: mix(#000, $black-box, 20%);

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