#191719

CSS

:root {
  --piano-black: #191719;
  --piano-black-rgb: 25 23 25;
  --piano-black-oklch: oklch(0.208 0.005 325.8);
}

.element {
  color: var(--piano-black);
  background-color: hsl(300 4% 9%);
  border-color: oklch(0.208 0.005 325.8);
}

Tailwind CSS v4

@theme {
  --color-piano-black: #191719;
  --color-piano-black-50: #f6f5f6;
  --color-piano-black-100: #e9e7e9;
  --color-piano-black-200: #d5d3d5;
  --color-piano-black-300: #b9b6b9;
  --color-piano-black-400: #a09da0;
  --color-piano-black-500: #888588;
  --color-piano-black-600: #737173;
  --color-piano-black-700: #5c5a5c;
  --color-piano-black-800: #434243;
  --color-piano-black-900: #2e2d2e;
  --color-piano-black-950: #1b1a1b;
}

SCSS

$piano-black: #191719;
$piano-black-rgb: 25, 23, 25;
$piano-black-light: mix(#fff, $piano-black, 20%);
$piano-black-dark: mix(#000, $piano-black, 20%);

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