#3C6CB3

CSS

:root {
  --matt-blue: #3c6cb3;
  --matt-blue-rgb: 60 108 179;
  --matt-blue-oklch: oklch(0.533 0.124 258.1);
}

.element {
  color: var(--matt-blue);
  background-color: hsl(216 50% 47%);
  border-color: oklch(0.533 0.124 258.1);
}

Tailwind CSS v4

@theme {
  --color-matt-blue: #3c6cb3;
  --color-matt-blue-50: #e1f7ff;
  --color-matt-blue-100: #d0e9ff;
  --color-matt-blue-200: #b6d6ff;
  --color-matt-blue-300: #92b8f7;
  --color-matt-blue-400: #70a0e7;
  --color-matt-blue-500: #4f86d7;
  --color-matt-blue-600: #4472b5;
  --color-matt-blue-700: #365b92;
  --color-matt-blue-800: #24436c;
  --color-matt-blue-900: #182e4c;
  --color-matt-blue-950: #091b32;
}

SCSS

$matt-blue: #3c6cb3;
$matt-blue-rgb: 60, 108, 179;
$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);
}