#356FAA

CSS

:root {
  --matt-blue: #356faa;
  --matt-blue-rgb: 53 111 170;
  --matt-blue-oklch: oklch(0.531 0.111 251);
}

.element {
  color: var(--matt-blue);
  background-color: hsl(210 52% 44%);
  border-color: oklch(0.531 0.111 251);
}

Tailwind CSS v4

@theme {
  --color-matt-blue: #356faa;
  --color-matt-blue-50: #dff8ff;
  --color-matt-blue-100: #ceebff;
  --color-matt-blue-200: #b3d8ff;
  --color-matt-blue-300: #8fbbef;
  --color-matt-blue-400: #6ba3de;
  --color-matt-blue-500: #488acd;
  --color-matt-blue-600: #3e75ad;
  --color-matt-blue-700: #315d8b;
  --color-matt-blue-800: #204567;
  --color-matt-blue-900: #153048;
  --color-matt-blue-950: #071c2f;
}

SCSS

$matt-blue: #356faa;
$matt-blue-rgb: 53, 111, 170;
$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);
}