#276EB5

CSS

:root {
  --matt-blue: #276eb5;
  --matt-blue-rgb: 39 110 181;
  --matt-blue-oklch: oklch(0.531 0.132 251.8);
}

.element {
  color: var(--matt-blue);
  background-color: hsl(210 65% 43%);
  border-color: oklch(0.531 0.132 251.8);
}

Tailwind CSS v4

@theme {
  --color-matt-blue: #276eb5;
  --color-matt-blue-50: #dcf8ff;
  --color-matt-blue-100: #caebff;
  --color-matt-blue-200: #add8ff;
  --color-matt-blue-300: #87bbfa;
  --color-matt-blue-400: #61a2ea;
  --color-matt-blue-500: #3a89da;
  --color-matt-blue-600: #3374b8;
  --color-matt-blue-700: #285d94;
  --color-matt-blue-800: #18446e;
  --color-matt-blue-900: #102f4d;
  --color-matt-blue-950: #031c33;
}

SCSS

$matt-blue: #276eb5;
$matt-blue-rgb: 39, 110, 181;
$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);
}