#3B6CB6

CSS

:root {
  --matt-blue: #3b6cb6;
  --matt-blue-rgb: 59 108 182;
  --matt-blue-oklch: oklch(0.534 0.128 258.5);
}

.element {
  color: var(--matt-blue);
  background-color: hsl(216 51% 47%);
  border-color: oklch(0.534 0.128 258.5);
}

Tailwind CSS v4

@theme {
  --color-matt-blue: #3b6cb6;
  --color-matt-blue-50: #e0f7ff;
  --color-matt-blue-100: #d0e9ff;
  --color-matt-blue-200: #b5d6ff;
  --color-matt-blue-300: #91b8f9;
  --color-matt-blue-400: #6e9fea;
  --color-matt-blue-500: #4e86da;
  --color-matt-blue-600: #4371b8;
  --color-matt-blue-700: #355b94;
  --color-matt-blue-800: #23436e;
  --color-matt-blue-900: #172e4d;
  --color-matt-blue-950: #081a33;
}

SCSS

$matt-blue: #3b6cb6;
$matt-blue-rgb: 59, 108, 182;
$matt-blue-light: mix(#fff, $matt-blue, 20%);
$matt-blue-dark: mix(#000, $matt-blue, 20%);

.element {
  color: $matt-blue;
  box-shadow: 0 0 0 2px rgba($matt-blue, 0.35);
}