#5C75A0

CSS

:root {
  --montreux-blue: #5c75a0;
  --montreux-blue-rgb: 92 117 160;
  --montreux-blue-oklch: oklch(0.56 0.073 261);
}

.element {
  color: var(--montreux-blue);
  background-color: hsl(218 27% 49%);
  border-color: oklch(0.56 0.073 261);
}

Tailwind CSS v4

@theme {
  --color-montreux-blue: #5c75a0;
  --color-montreux-blue-50: #eaf6ff;
  --color-montreux-blue-100: #dbe8ff;
  --color-montreux-blue-200: #c4d5f5;
  --color-montreux-blue-300: #a4b8de;
  --color-montreux-blue-400: #869fca;
  --color-montreux-blue-500: #6a87b7;
  --color-montreux-blue-600: #5a729b;
  --color-montreux-blue-700: #485b7c;
  --color-montreux-blue-800: #33435c;
  --color-montreux-blue-900: #232e40;
  --color-montreux-blue-950: #121b29;
}

SCSS

$montreux-blue: #5c75a0;
$montreux-blue-rgb: 92, 117, 160;
$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);
}