#3FA7BF

CSS

:root {
  --true-sky-blue: #3fa7bf;
  --true-sky-blue-rgb: 63 167 191;
  --true-sky-blue-oklch: oklch(0.678 0.1 216);
}

.element {
  color: var(--true-sky-blue);
  background-color: hsl(191 50% 50%);
  border-color: oklch(0.678 0.1 216);
}

Tailwind CSS v4

@theme {
  --color-true-sky-blue: #3fa7bf;
  --color-true-sky-blue-50: #d6fdff;
  --color-true-sky-blue-100: #c4f1fe;
  --color-true-sky-blue-200: #a4dff1;
  --color-true-sky-blue-300: #7ac4d9;
  --color-true-sky-blue-400: #4eadc4;
  --color-true-sky-blue-500: #0296b0;
  --color-true-sky-blue-600: #0e7f95;
  --color-true-sky-blue-700: #0d6677;
  --color-true-sky-blue-800: #054b57;
  --color-true-sky-blue-900: #04343d;
  --color-true-sky-blue-950: #001f27;
}

SCSS

$true-sky-blue: #3fa7bf;
$true-sky-blue-rgb: 63, 167, 191;
$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);
}