#51A3D1

CSS

:root {
  --sub-zero: #51a3d1;
  --sub-zero-rgb: 81 163 209;
  --sub-zero-oklch: oklch(0.683 0.105 235.7);
}

.element {
  color: var(--sub-zero);
  background-color: hsl(202 58% 57%);
  border-color: oklch(0.683 0.105 235.7);
}

Tailwind CSS v4

@theme {
  --color-sub-zero: #51a3d1;
  --color-sub-zero-50: #dafaff;
  --color-sub-zero-100: #c8eeff;
  --color-sub-zero-200: #abdcfc;
  --color-sub-zero-300: #83c0e7;
  --color-sub-zero-400: #5ba8d4;
  --color-sub-zero-500: #2f90c2;
  --color-sub-zero-600: #2a7aa4;
  --color-sub-zero-700: #216283;
  --color-sub-zero-800: #144861;
  --color-sub-zero-900: #0d3244;
  --color-sub-zero-950: #011e2c;
}

SCSS

$sub-zero: #51a3d1;
$sub-zero-rgb: 81, 163, 209;
$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);
}