#2A0240

CSS

:root {
  --your-darkness: #2a0240;
  --your-darkness-rgb: 42 2 64;
  --your-darkness-oklch: oklch(0.223 0.109 309.2);
}

.element {
  color: var(--your-darkness);
  background-color: hsl(279 94% 13%);
  border-color: oklch(0.223 0.109 309.2);
}

Tailwind CSS v4

@theme {
  --color-your-darkness: #2a0240;
  --color-your-darkness-50: #ffedff;
  --color-your-darkness-100: #f4deff;
  --color-your-darkness-200: #e3c8f7;
  --color-your-darkness-300: #c9a8e1;
  --color-your-darkness-400: #b18ccf;
  --color-your-darkness-500: #9b71bc;
  --color-your-darkness-600: #83609f;
  --color-your-darkness-700: #694c80;
  --color-your-darkness-800: #4c3860;
  --color-your-darkness-900: #352643;
  --color-your-darkness-950: #20142b;
}

SCSS

$your-darkness: #2a0240;
$your-darkness-rgb: 42, 2, 64;
$your-darkness-light: mix(#fff, $your-darkness, 20%);
$your-darkness-dark: mix(#000, $your-darkness, 20%);

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