#80D1F6

CSS

:root {
  --below-zero: #80d1f6;
  --below-zero-rgb: 128 209 246;
  --below-zero-oklch: oklch(0.822 0.095 229);
}

.element {
  color: var(--below-zero);
  background-color: hsl(199 87% 73%);
  border-color: oklch(0.822 0.095 229);
}

Tailwind CSS v4

@theme {
  --color-below-zero: #80d1f6;
  --color-below-zero-50: #dbfbff;
  --color-below-zero-100: #c9eeff;
  --color-below-zero-200: #acdcf6;
  --color-below-zero-300: #84c1df;
  --color-below-zero-400: #5da9cb;
  --color-below-zero-500: #3292b8;
  --color-below-zero-600: #2c7b9b;
  --color-below-zero-700: #23637d;
  --color-below-zero-800: #16495c;
  --color-below-zero-900: #0e3240;
  --color-below-zero-950: #021e29;
}

SCSS

$below-zero: #80d1f6;
$below-zero-rgb: 128, 209, 246;
$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);
}