#3A6ABE

CSS

:root {
  --matt-blue: #3a6abe;
  --matt-blue-rgb: 58 106 190;
  --matt-blue-oklch: oklch(0.534 0.142 260.7);
}

.element {
  color: var(--matt-blue);
  background-color: hsl(218 53% 49%);
  border-color: oklch(0.534 0.142 260.7);
}

Tailwind CSS v4

@theme {
  --color-matt-blue: #3a6abe;
  --color-matt-blue-50: #e0f6ff;
  --color-matt-blue-100: #cfe9ff;
  --color-matt-blue-200: #b4d5ff;
  --color-matt-blue-300: #90b7ff;
  --color-matt-blue-400: #6d9ef2;
  --color-matt-blue-500: #4d83e3;
  --color-matt-blue-600: #416fbf;
  --color-matt-blue-700: #34599a;
  --color-matt-blue-800: #224273;
  --color-matt-blue-900: #162d51;
  --color-matt-blue-950: #071a36;
}

SCSS

$matt-blue: #3a6abe;
$matt-blue-rgb: 58, 106, 190;
$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);
}