#0091EE

CSS

:root {
  --out-of-the-blue: #0091ee;
  --out-of-the-blue-rgb: 0 145 238;
  --out-of-the-blue-oklch: oklch(0.641 0.172 247.8);
}

.element {
  color: var(--out-of-the-blue);
  background-color: hsl(203 100% 47%);
  border-color: oklch(0.641 0.172 247.8);
}

Tailwind CSS v4

@theme {
  --color-out-of-the-blue: #0091ee;
  --color-out-of-the-blue-50: #d0faff;
  --color-out-of-the-blue-100: #bcedff;
  --color-out-of-the-blue-200: #9bdaff;
  --color-out-of-the-blue-300: #6ebdff;
  --color-out-of-the-blue-400: #37a4fe;
  --color-out-of-the-blue-500: #008af0;
  --color-out-of-the-blue-600: #0075cb;
  --color-out-of-the-blue-700: #005ea3;
  --color-out-of-the-blue-800: #004579;
  --color-out-of-the-blue-900: #003056;
  --color-out-of-the-blue-950: #001c3a;
}

SCSS

$out-of-the-blue: #0091ee;
$out-of-the-blue-rgb: 0, 145, 238;
$out-of-the-blue-light: mix(#fff, $out-of-the-blue, 20%);
$out-of-the-blue-dark: mix(#000, $out-of-the-blue, 20%);

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