#5876A4

CSS

:root {
  --montreux-blue: #5876a4;
  --montreux-blue-rgb: 88 118 164;
  --montreux-blue-oklch: oklch(0.562 0.08 258.7);
}

.element {
  color: var(--montreux-blue);
  background-color: hsl(216 30% 49%);
  border-color: oklch(0.562 0.08 258.7);
}

Tailwind CSS v4

@theme {
  --color-montreux-blue: #5876a4;
  --color-montreux-blue-50: #e8f6ff;
  --color-montreux-blue-100: #d9e9ff;
  --color-montreux-blue-200: #c1d5f7;
  --color-montreux-blue-300: #a0b8e1;
  --color-montreux-blue-400: #82a0ce;
  --color-montreux-blue-500: #6587bb;
  --color-montreux-blue-600: #56739e;
  --color-montreux-blue-700: #455c7f;
  --color-montreux-blue-800: #30435e;
  --color-montreux-blue-900: #212e42;
  --color-montreux-blue-950: #101b2a;
}

SCSS

$montreux-blue: #5876a4;
$montreux-blue-rgb: 88, 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);
}