#2A2439

CSS

:root {
  --black-velvet: #2a2439;
  --black-velvet-rgb: 42 36 57;
  --black-velvet-oklch: oklch(0.277 0.039 296.9);
}

.element {
  color: var(--black-velvet);
  background-color: hsl(257 23% 18%);
  border-color: oklch(0.277 0.039 296.9);
}

Tailwind CSS v4

@theme {
  --color-black-velvet: #2a2439;
  --color-black-velvet-50: #f6f3ff;
  --color-black-velvet-100: #e9e5f3;
  --color-black-velvet-200: #d6d1e3;
  --color-black-velvet-300: #bab3c9;
  --color-black-velvet-400: #a09ab3;
  --color-black-velvet-500: #88819d;
  --color-black-velvet-600: #736d85;
  --color-black-velvet-700: #5c576b;
  --color-black-velvet-800: #43404f;
  --color-black-velvet-900: #2e2c37;
  --color-black-velvet-950: #1b1922;
}

SCSS

$black-velvet: #2a2439;
$black-velvet-rgb: 42, 36, 57;
$black-velvet-light: mix(#fff, $black-velvet, 20%);
$black-velvet-dark: mix(#000, $black-velvet, 20%);

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