#366CBB

CSS

:root {
  --matt-blue: #366cbb;
  --matt-blue-rgb: 54 108 187;
  --matt-blue-oklch: oklch(0.535 0.137 258);
}

.element {
  color: var(--matt-blue);
  background-color: hsl(216 55% 47%);
  border-color: oklch(0.535 0.137 258);
}

Tailwind CSS v4

@theme {
  --color-matt-blue: #366cbb;
  --color-matt-blue-50: #dff7ff;
  --color-matt-blue-100: #cee9ff;
  --color-matt-blue-200: #b2d6ff;
  --color-matt-blue-300: #8eb8fd;
  --color-matt-blue-400: #6a9fee;
  --color-matt-blue-500: #4885df;
  --color-matt-blue-600: #3e71bc;
  --color-matt-blue-700: #315a97;
  --color-matt-blue-800: #1f4371;
  --color-matt-blue-900: #152e4f;
  --color-matt-blue-950: #061a35;
}

SCSS

$matt-blue: #366cbb;
$matt-blue-rgb: 54, 108, 187;
$matt-blue-light: mix(#fff, $matt-blue, 20%);
$matt-blue-dark: mix(#000, $matt-blue, 20%);

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