#002A34

CSS

:root {
  --black-box: #002a34;
  --black-box-rgb: 0 42 52;
  --black-box-oklch: oklch(0.263 0.047 218.2);
}

.element {
  color: var(--black-box);
  background-color: hsl(192 100% 10%);
  border-color: oklch(0.263 0.047 218.2);
}

Tailwind CSS v4

@theme {
  --color-black-box: #002a34;
  --color-black-box-50: #e7f9ff;
  --color-black-box-100: #d8ecf3;
  --color-black-box-200: #bfd9e2;
  --color-black-box-300: #9ebec8;
  --color-black-box-400: #7fa6b1;
  --color-black-box-500: #628e9b;
  --color-black-box-600: #537883;
  --color-black-box-700: #426069;
  --color-black-box-800: #2f474d;
  --color-black-box-900: #203135;
  --color-black-box-950: #0f1d21;
}

SCSS

$black-box: #002a34;
$black-box-rgb: 0, 42, 52;
$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);
}