#3B6DAE

CSS

:root {
  --matt-blue: #3b6dae;
  --matt-blue-rgb: 59 109 174;
  --matt-blue-oklch: oklch(0.531 0.116 255.8);
}

.element {
  color: var(--matt-blue);
  background-color: hsl(214 49% 46%);
  border-color: oklch(0.531 0.116 255.8);
}

Tailwind CSS v4

@theme {
  --color-matt-blue: #3b6dae;
  --color-matt-blue-50: #e1f7ff;
  --color-matt-blue-100: #d0eaff;
  --color-matt-blue-200: #b6d6ff;
  --color-matt-blue-300: #92b9f3;
  --color-matt-blue-400: #6fa1e2;
  --color-matt-blue-500: #4f87d2;
  --color-matt-blue-600: #4373b1;
  --color-matt-blue-700: #365c8e;
  --color-matt-blue-800: #24446a;
  --color-matt-blue-900: #182f4a;
  --color-matt-blue-950: #081b31;
}

SCSS

$matt-blue: #3b6dae;
$matt-blue-rgb: 59, 109, 174;
$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);
}