#002830

CSS

:root {
  --black-box: #002830;
  --black-box-rgb: 0 40 48;
  --black-box-oklch: oklch(0.255 0.045 214.5);
}

.element {
  color: var(--black-box);
  background-color: hsl(190 100% 9%);
  border-color: oklch(0.255 0.045 214.5);
}

Tailwind CSS v4

@theme {
  --color-black-box: #002830;
  --color-black-box-50: #e8f9fd;
  --color-black-box-100: #d8ecf2;
  --color-black-box-200: #c0d9e1;
  --color-black-box-300: #9ebec6;
  --color-black-box-400: #81a6af;
  --color-black-box-500: #638e99;
  --color-black-box-600: #557881;
  --color-black-box-700: #436067;
  --color-black-box-800: #30474c;
  --color-black-box-900: #213134;
  --color-black-box-950: #101d20;
}

SCSS

$black-box: #002830;
$black-box-rgb: 0, 40, 48;
$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);
}