#BF4300

CSS

:root {
  --copper-hopper: #bf4300;
  --copper-hopper-rgb: 191 67 0;
  --copper-hopper-oklch: oklch(0.55 0.17 40.7);
}

.element {
  color: var(--copper-hopper);
  background-color: hsl(21 100% 37%);
  border-color: oklch(0.55 0.17 40.7);
}

Tailwind CSS v4

@theme {
  --color-copper-hopper: #bf4300;
  --color-copper-hopper-50: #ffe6cf;
  --color-copper-hopper-100: #ffd6bb;
  --color-copper-hopper-200: #ffbc9a;
  --color-copper-hopper-300: #ff986e;
  --color-copper-hopper-400: #f07648;
  --color-copper-hopper-500: #de520c;
  --color-copper-hopper-600: #bc4711;
  --color-copper-hopper-700: #97380e;
  --color-copper-hopper-800: #71270c;
  --color-copper-hopper-900: #501a08;
  --color-copper-hopper-950: #350a00;
}

SCSS

$copper-hopper: #bf4300;
$copper-hopper-rgb: 191, 67, 0;
$copper-hopper-light: mix(#fff, $copper-hopper, 20%);
$copper-hopper-dark: mix(#000, $copper-hopper, 20%);

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