#3B6DB2

CSS

:root {
  --matt-blue: #3b6db2;
  --matt-blue-rgb: 59 109 178;
  --matt-blue-oklch: oklch(0.534 0.122 256.9);
}

.element {
  color: var(--matt-blue);
  background-color: hsl(215 50% 46%);
  border-color: oklch(0.534 0.122 256.9);
}

Tailwind CSS v4

@theme {
  --color-matt-blue: #3b6db2;
  --color-matt-blue-50: #e1f7ff;
  --color-matt-blue-100: #d0eaff;
  --color-matt-blue-200: #b5d6ff;
  --color-matt-blue-300: #92b9f6;
  --color-matt-blue-400: #6fa0e5;
  --color-matt-blue-500: #4e87d5;
  --color-matt-blue-600: #4372b4;
  --color-matt-blue-700: #355b91;
  --color-matt-blue-800: #23436b;
  --color-matt-blue-900: #172e4c;
  --color-matt-blue-950: #081b32;
}

SCSS

$matt-blue: #3b6db2;
$matt-blue-rgb: 59, 109, 178;
$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);
}