#366FAB

CSS

:root {
  --matt-blue: #366fab;
  --matt-blue-rgb: 54 111 171;
  --matt-blue-oklch: oklch(0.532 0.112 251.7);
}

.element {
  color: var(--matt-blue);
  background-color: hsl(211 52% 44%);
  border-color: oklch(0.532 0.112 251.7);
}

Tailwind CSS v4

@theme {
  --color-matt-blue: #366fab;
  --color-matt-blue-50: #e0f8ff;
  --color-matt-blue-100: #cfebff;
  --color-matt-blue-200: #b3d8ff;
  --color-matt-blue-300: #8fbbf0;
  --color-matt-blue-400: #6ca2df;
  --color-matt-blue-500: #4989ce;
  --color-matt-blue-600: #3f74ae;
  --color-matt-blue-700: #325d8c;
  --color-matt-blue-800: #214567;
  --color-matt-blue-900: #162f49;
  --color-matt-blue-950: #071c30;
}

SCSS

$matt-blue: #366fab;
$matt-blue-rgb: 54, 111, 171;
$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);
}