#5B70A3

CSS

:root {
  --loch-ness: #5b70a3;
  --loch-ness-rgb: 91 112 163;
  --loch-ness-oklch: oklch(0.55 0.084 266.6);
}

.element {
  color: var(--loch-ness);
  background-color: hsl(223 28% 50%);
  border-color: oklch(0.55 0.084 266.6);
}

Tailwind CSS v4

@theme {
  --color-loch-ness: #5b70a3;
  --color-loch-ness-50: #ebf5ff;
  --color-loch-ness-100: #dce8ff;
  --color-loch-ness-200: #c5d4f9;
  --color-loch-ness-300: #a5b6e3;
  --color-loch-ness-400: #889dd1;
  --color-loch-ness-500: #6d84be;
  --color-loch-ness-600: #5c70a1;
  --color-loch-ness-700: #495a81;
  --color-loch-ness-800: #344260;
  --color-loch-ness-900: #232d43;
  --color-loch-ness-950: #121a2b;
}

SCSS

$loch-ness: #5b70a3;
$loch-ness-rgb: 91, 112, 163;
$loch-ness-light: mix(#fff, $loch-ness, 20%);
$loch-ness-dark: mix(#000, $loch-ness, 20%);

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