#66A1C8

CSS

:root {
  --sub-zero: #66a1c8;
  --sub-zero-rgb: 102 161 200;
  --sub-zero-oklch: oklch(0.684 0.084 238.7);
}

.element {
  color: var(--sub-zero);
  background-color: hsl(204 47% 59%);
  border-color: oklch(0.684 0.084 238.7);
}

Tailwind CSS v4

@theme {
  --color-sub-zero: #66a1c8;
  --color-sub-zero-50: #e1f9ff;
  --color-sub-zero-100: #d0ecff;
  --color-sub-zero-200: #b5daf5;
  --color-sub-zero-300: #91bedf;
  --color-sub-zero-400: #6ea6cb;
  --color-sub-zero-500: #4c8eb8;
  --color-sub-zero-600: #41789b;
  --color-sub-zero-700: #34607d;
  --color-sub-zero-800: #23475c;
  --color-sub-zero-900: #173140;
  --color-sub-zero-950: #081d29;
}

SCSS

$sub-zero: #66a1c8;
$sub-zero-rgb: 102, 161, 200;
$sub-zero-light: mix(#fff, $sub-zero, 20%);
$sub-zero-dark: mix(#000, $sub-zero, 20%);

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