#00252A

CSS

:root {
  --black-box: #00252a;
  --black-box-rgb: 0 37 42;
  --black-box-oklch: oklch(0.242 0.042 208.1);
}

.element {
  color: var(--black-box);
  background-color: hsl(187 100% 8%);
  border-color: oklch(0.242 0.042 208.1);
}

Tailwind CSS v4

@theme {
  --color-black-box: #00252a;
  --color-black-box-50: #e8f9fc;
  --color-black-box-100: #d9ecf0;
  --color-black-box-200: #c1d9de;
  --color-black-box-300: #a0bec3;
  --color-black-box-400: #82a6ab;
  --color-black-box-500: #668e95;
  --color-black-box-600: #56787e;
  --color-black-box-700: #456065;
  --color-black-box-800: #314749;
  --color-black-box-900: #213133;
  --color-black-box-950: #111d1f;
}

SCSS

$black-box: #00252a;
$black-box-rgb: 0, 37, 42;
$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);
}