#5676A5

CSS

:root {
  --montreux-blue: #5676a5;
  --montreux-blue-rgb: 86 118 165;
  --montreux-blue-oklch: oklch(0.561 0.082 257.9);
}

.element {
  color: var(--montreux-blue);
  background-color: hsl(216 31% 49%);
  border-color: oklch(0.561 0.082 257.9);
}

Tailwind CSS v4

@theme {
  --color-montreux-blue: #5676a5;
  --color-montreux-blue-50: #e8f6ff;
  --color-montreux-blue-100: #d8e9ff;
  --color-montreux-blue-200: #c0d6f8;
  --color-montreux-blue-300: #9fb9e2;
  --color-montreux-blue-400: #80a0cf;
  --color-montreux-blue-500: #6388bd;
  --color-montreux-blue-600: #55739f;
  --color-montreux-blue-700: #435c80;
  --color-montreux-blue-800: #2f435f;
  --color-montreux-blue-900: #202f42;
  --color-montreux-blue-950: #0f1b2b;
}

SCSS

$montreux-blue: #5676a5;
$montreux-blue-rgb: 86, 118, 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);
}