#C03A00

CSS

:root {
  --copper-hopper: #c03a00;
  --copper-hopper-rgb: 192 58 0;
  --copper-hopper-oklch: oklch(0.542 0.179 37.6);
}

.element {
  color: var(--copper-hopper);
  background-color: hsl(18 100% 38%);
  border-color: oklch(0.542 0.179 37.6);
}

Tailwind CSS v4

@theme {
  --color-copper-hopper: #c03a00;
  --color-copper-hopper-50: #ffe5cf;
  --color-copper-hopper-100: #ffd4bb;
  --color-copper-hopper-200: #ffba9a;
  --color-copper-hopper-300: #ff956f;
  --color-copper-hopper-400: #f4724a;
  --color-copper-hopper-500: #e34c13;
  --color-copper-hopper-600: #bf4115;
  --color-copper-hopper-700: #9a3411;
  --color-copper-hopper-800: #73240e;
  --color-copper-hopper-900: #511809;
  --color-copper-hopper-950: #360800;
}

SCSS

$copper-hopper: #c03a00;
$copper-hopper-rgb: 192, 58, 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);
}