#16151F

CSS

:root {
  --back-in-black: #16151f;
  --back-in-black-rgb: 22 21 31;
  --back-in-black-oklch: oklch(0.202 0.02 289.1);
}

.element {
  color: var(--back-in-black);
  background-color: hsl(246 19% 10%);
  border-color: oklch(0.202 0.02 289.1);
}

Tailwind CSS v4

@theme {
  --color-back-in-black: #16151f;
  --color-back-in-black-50: #f5f4fb;
  --color-back-in-black-100: #e8e7ee;
  --color-back-in-black-200: #d4d3dc;
  --color-back-in-black-300: #b7b6c1;
  --color-back-in-black-400: #9e9daa;
  --color-back-in-black-500: #858493;
  --color-back-in-black-600: #71707c;
  --color-back-in-black-700: #5a5a63;
  --color-back-in-black-800: #424149;
  --color-back-in-black-900: #2d2d33;
  --color-back-in-black-950: #1a1a1e;
}

SCSS

$back-in-black: #16151f;
$back-in-black-rgb: 22, 21, 31;
$back-in-black-light: mix(#fff, $back-in-black, 20%);
$back-in-black-dark: mix(#000, $back-in-black, 20%);

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