#5C75A5

CSS

:root {
  --montreux-blue: #5c75a5;
  --montreux-blue-rgb: 92 117 165;
  --montreux-blue-oklch: oklch(0.563 0.081 262.9);
}

.element {
  color: var(--montreux-blue);
  background-color: hsl(219 29% 50%);
  border-color: oklch(0.563 0.081 262.9);
}

Tailwind CSS v4

@theme {
  --color-montreux-blue: #5c75a5;
  --color-montreux-blue-50: #eaf5ff;
  --color-montreux-blue-100: #dbe8ff;
  --color-montreux-blue-200: #c3d4f8;
  --color-montreux-blue-300: #a3b7e2;
  --color-montreux-blue-400: #859fcf;
  --color-montreux-blue-500: #6a86bc;
  --color-montreux-blue-600: #5a719f;
  --color-montreux-blue-700: #475b7f;
  --color-montreux-blue-800: #32435e;
  --color-montreux-blue-900: #222e42;
  --color-montreux-blue-950: #111b2b;
}

SCSS

$montreux-blue: #5c75a5;
$montreux-blue-rgb: 92, 117, 165;
$montreux-blue-light: mix(#fff, $montreux-blue, 20%);
$montreux-blue-dark: mix(#000, $montreux-blue, 20%);

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