#399EB7

CSS

:root {
  --true-sky-blue: #399eb7;
  --true-sky-blue-rgb: 57 158 183;
  --true-sky-blue-oklch: oklch(0.652 0.098 217.5);
}

.element {
  color: var(--true-sky-blue);
  background-color: hsl(192 53% 47%);
  border-color: oklch(0.652 0.098 217.5);
}

Tailwind CSS v4

@theme {
  --color-true-sky-blue: #399eb7;
  --color-true-sky-blue-50: #d7fdff;
  --color-true-sky-blue-100: #c5f0ff;
  --color-true-sky-blue-200: #a5dff1;
  --color-true-sky-blue-300: #7cc4da;
  --color-true-sky-blue-400: #51adc5;
  --color-true-sky-blue-500: #1295b1;
  --color-true-sky-blue-600: #167e95;
  --color-true-sky-blue-700: #136578;
  --color-true-sky-blue-800: #094b58;
  --color-true-sky-blue-900: #06343d;
  --color-true-sky-blue-950: #001f27;
}

SCSS

$true-sky-blue: #399eb7;
$true-sky-blue-rgb: 57, 158, 183;
$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);
}