#3F6BB5

CSS

:root {
  --matt-blue: #3f6bb5;
  --matt-blue-rgb: 63 107 181;
  --matt-blue-oklch: oklch(0.533 0.126 260.2);
}

.element {
  color: var(--matt-blue);
  background-color: hsl(218 48% 48%);
  border-color: oklch(0.533 0.126 260.2);
}

Tailwind CSS v4

@theme {
  --color-matt-blue: #3f6bb5;
  --color-matt-blue-50: #e2f6ff;
  --color-matt-blue-100: #d1e9ff;
  --color-matt-blue-200: #b7d5ff;
  --color-matt-blue-300: #94b8f9;
  --color-matt-blue-400: #729fe9;
  --color-matt-blue-500: #5385d9;
  --color-matt-blue-600: #4670b7;
  --color-matt-blue-700: #385a93;
  --color-matt-blue-800: #25426d;
  --color-matt-blue-900: #192e4d;
  --color-matt-blue-950: #0a1a33;
}

SCSS

$matt-blue: #3f6bb5;
$matt-blue-rgb: 63, 107, 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);
}