#5F7B86

CSS

:root {
  --night-owl: #5f7b86;
  --night-owl-rgb: 95 123 134;
  --night-owl-oklch: oklch(0.565 0.036 223.9);
}

.element {
  color: var(--night-owl);
  background-color: hsl(197 17% 45%);
  border-color: oklch(0.565 0.036 223.9);
}

Tailwind CSS v4

@theme {
  --color-night-owl: #5f7b86;
  --color-night-owl-50: #ebf8fd;
  --color-night-owl-100: #dcebf1;
  --color-night-owl-200: #c5d8e0;
  --color-night-owl-300: #a5bcc6;
  --color-night-owl-400: #88a4af;
  --color-night-owl-500: #6c8c98;
  --color-night-owl-600: #5c7681;
  --color-night-owl-700: #495f67;
  --color-night-owl-800: #35454b;
  --color-night-owl-900: #243034;
  --color-night-owl-950: #131c20;
}

SCSS

$night-owl: #5f7b86;
$night-owl-rgb: 95, 123, 134;
$night-owl-light: mix(#fff, $night-owl, 20%);
$night-owl-dark: mix(#000, $night-owl, 20%);

.element {
  color: $night-owl;
  box-shadow: 0 0 0 2px rgba($night-owl, 0.35);
}