#5F74A5

CSS

:root {
  --misty-harbour: #5f74a5;
  --misty-harbour-rgb: 95 116 165;
  --misty-harbour-oklch: oklch(0.563 0.08 266.1);
}

.element {
  color: var(--misty-harbour);
  background-color: hsl(222 28% 51%);
  border-color: oklch(0.563 0.08 266.1);
}

Tailwind CSS v4

@theme {
  --color-misty-harbour: #5f74a5;
  --color-misty-harbour-50: #ebf5ff;
  --color-misty-harbour-100: #dce8ff;
  --color-misty-harbour-200: #c5d4f8;
  --color-misty-harbour-300: #a6b7e2;
  --color-misty-harbour-400: #889ecf;
  --color-misty-harbour-500: #6d85bc;
  --color-misty-harbour-600: #5d709f;
  --color-misty-harbour-700: #4a5a7f;
  --color-misty-harbour-800: #34425e;
  --color-misty-harbour-900: #232e42;
  --color-misty-harbour-950: #121a2b;
}

SCSS

$misty-harbour: #5f74a5;
$misty-harbour-rgb: 95, 116, 165;
$misty-harbour-light: mix(#fff, $misty-harbour, 20%);
$misty-harbour-dark: mix(#000, $misty-harbour, 20%);

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