#51A6BC

CSS

:root {
  --true-sky-blue: #51a6bc;
  --true-sky-blue-rgb: 81 166 188;
  --true-sky-blue-oklch: oklch(0.681 0.088 217.1);
}

.element {
  color: var(--true-sky-blue);
  background-color: hsl(192 44% 53%);
  border-color: oklch(0.681 0.088 217.1);
}

Tailwind CSS v4

@theme {
  --color-true-sky-blue: #51a6bc;
  --color-true-sky-blue-50: #dafcff;
  --color-true-sky-blue-100: #c8f0fc;
  --color-true-sky-blue-200: #abdeee;
  --color-true-sky-blue-300: #83c3d6;
  --color-true-sky-blue-400: #5cabc0;
  --color-true-sky-blue-500: #2f94ac;
  --color-true-sky-blue-600: #2a7d91;
  --color-true-sky-blue-700: #226475;
  --color-true-sky-blue-800: #154a55;
  --color-true-sky-blue-900: #0e333c;
  --color-true-sky-blue-950: #011f25;
}

SCSS

$true-sky-blue: #51a6bc;
$true-sky-blue-rgb: 81, 166, 188;
$true-sky-blue-light: mix(#fff, $true-sky-blue, 20%);
$true-sky-blue-dark: mix(#000, $true-sky-blue, 20%);

.element {
  color: $true-sky-blue;
  box-shadow: 0 0 0 2px rgba($true-sky-blue, 0.35);
}