#3B6EAA

CSS

:root {
  --matt-blue: #3b6eaa;
  --matt-blue-rgb: 59 110 170;
  --matt-blue-oklch: oklch(0.531 0.11 253.8);
}

.element {
  color: var(--matt-blue);
  background-color: hsl(212 48% 45%);
  border-color: oklch(0.531 0.11 253.8);
}

Tailwind CSS v4

@theme {
  --color-matt-blue: #3b6eaa;
  --color-matt-blue-50: #e1f7ff;
  --color-matt-blue-100: #d0eaff;
  --color-matt-blue-200: #b6d7ff;
  --color-matt-blue-300: #92baef;
  --color-matt-blue-400: #70a2de;
  --color-matt-blue-500: #4f89cd;
  --color-matt-blue-600: #4374ad;
  --color-matt-blue-700: #365d8b;
  --color-matt-blue-800: #244467;
  --color-matt-blue-900: #182f48;
  --color-matt-blue-950: #081b2f;
}

SCSS

$matt-blue: #3b6eaa;
$matt-blue-rgb: 59, 110, 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);
}