#00252F

CSS

:root {
  --black-box: #00252f;
  --black-box-rgb: 0 37 47;
  --black-box-oklch: oklch(0.245 0.045 220.2);
}

.element {
  color: var(--black-box);
  background-color: hsl(193 100% 9%);
  border-color: oklch(0.245 0.045 220.2);
}

Tailwind CSS v4

@theme {
  --color-black-box: #00252f;
  --color-black-box-50: #e8f8fe;
  --color-black-box-100: #d9ecf3;
  --color-black-box-200: #c1d9e2;
  --color-black-box-300: #9fbdc8;
  --color-black-box-400: #82a5b1;
  --color-black-box-500: #658e9b;
  --color-black-box-600: #567883;
  --color-black-box-700: #446069;
  --color-black-box-800: #31464d;
  --color-black-box-900: #213135;
  --color-black-box-950: #101d20;
}

SCSS

$black-box: #00252f;
$black-box-rgb: 0, 37, 47;
$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);
}