#5C74A6

CSS

:root {
  --montreux-blue: #5c74a6;
  --montreux-blue-rgb: 92 116 166;
  --montreux-blue-oklch: oklch(0.561 0.083 264.2);
}

.element {
  color: var(--montreux-blue);
  background-color: hsl(221 29% 51%);
  border-color: oklch(0.561 0.083 264.2);
}

Tailwind CSS v4

@theme {
  --color-montreux-blue: #5c74a6;
  --color-montreux-blue-50: #eaf5ff;
  --color-montreux-blue-100: #dbe8ff;
  --color-montreux-blue-200: #c4d4f9;
  --color-montreux-blue-300: #a4b7e3;
  --color-montreux-blue-400: #869ed0;
  --color-montreux-blue-500: #6a85be;
  --color-montreux-blue-600: #5a71a0;
  --color-montreux-blue-700: #485a81;
  --color-montreux-blue-800: #33425f;
  --color-montreux-blue-900: #222e43;
  --color-montreux-blue-950: #121a2b;
}

SCSS

$montreux-blue: #5c74a6;
$montreux-blue-rgb: 92, 116, 166;
$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);
}