#5476A4

CSS

:root {
  --montreux-blue: #5476a4;
  --montreux-blue-rgb: 84 118 164;
  --montreux-blue-oklch: oklch(0.56 0.082 256.2);
}

.element {
  color: var(--montreux-blue);
  background-color: hsl(215 32% 49%);
  border-color: oklch(0.56 0.082 256.2);
}

Tailwind CSS v4

@theme {
  --color-montreux-blue: #5476a4;
  --color-montreux-blue-50: #e7f6ff;
  --color-montreux-blue-100: #d7e9ff;
  --color-montreux-blue-200: #bfd6f8;
  --color-montreux-blue-300: #9eb9e2;
  --color-montreux-blue-400: #7fa1cf;
  --color-montreux-blue-500: #6288bc;
  --color-montreux-blue-600: #53739f;
  --color-montreux-blue-700: #425c7f;
  --color-montreux-blue-800: #2e445e;
  --color-montreux-blue-900: #1f2f42;
  --color-montreux-blue-950: #0f1b2a;
}

SCSS

$montreux-blue: #5476a4;
$montreux-blue-rgb: 84, 118, 164;
$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);
}