#356FAC

CSS

:root {
  --matt-blue: #356fac;
  --matt-blue-rgb: 53 111 172;
  --matt-blue-oklch: oklch(0.532 0.114 251.8);
}

.element {
  color: var(--matt-blue);
  background-color: hsl(211 53% 44%);
  border-color: oklch(0.532 0.114 251.8);
}

Tailwind CSS v4

@theme {
  --color-matt-blue: #356fac;
  --color-matt-blue-50: #dff8ff;
  --color-matt-blue-100: #ceebff;
  --color-matt-blue-200: #b3d8ff;
  --color-matt-blue-300: #8fbbf1;
  --color-matt-blue-400: #6ba2e0;
  --color-matt-blue-500: #4889cf;
  --color-matt-blue-600: #3e74af;
  --color-matt-blue-700: #315d8c;
  --color-matt-blue-800: #204568;
  --color-matt-blue-900: #152f49;
  --color-matt-blue-950: #061c30;
}

SCSS

$matt-blue: #356fac;
$matt-blue-rgb: 53, 111, 172;
$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);
}