#81D3EF

CSS

:root {
  --below-zero: #81d3ef;
  --below-zero-rgb: 129 211 239;
  --below-zero-oklch: oklch(0.824 0.089 221.9);
}

.element {
  color: var(--below-zero);
  background-color: hsl(195 77% 72%);
  border-color: oklch(0.824 0.089 221.9);
}

Tailwind CSS v4

@theme {
  --color-below-zero: #81d3ef;
  --color-below-zero-50: #dbfbff;
  --color-below-zero-100: #c9effe;
  --color-below-zero-200: #acddf1;
  --color-below-zero-300: #84c2d9;
  --color-below-zero-400: #5eaac4;
  --color-below-zero-500: #3293b0;
  --color-below-zero-600: #2c7c95;
  --color-below-zero-700: #236477;
  --color-below-zero-800: #164958;
  --color-below-zero-900: #0f333d;
  --color-below-zero-950: #021e27;
}

SCSS

$below-zero: #81d3ef;
$below-zero-rgb: 129, 211, 239;
$below-zero-light: mix(#fff, $below-zero, 20%);
$below-zero-dark: mix(#000, $below-zero, 20%);

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