Blue

CSS

:root {
  --blue: #0000ff;
  --blue-rgb: 0 0 255;
  --blue-oklch: oklch(0.452 0.313 264.1);
}

.element {
  color: var(--blue);
  background-color: hsl(240 100% 50%);
  border-color: oklch(0.452 0.313 264.1);
}

Tailwind CSS v4

@theme {
  --color-blue: #0000ff;
  --color-blue-50: #cbf3ff;
  --color-blue-100: #b7e4ff;
  --color-blue-200: #95cdff;
  --color-blue-300: #6ba8ff;
  --color-blue-400: #3886ff;
  --color-blue-500: #0958ff;
  --color-blue-600: #0a4dff;
  --color-blue-700: #083ee4;
  --color-blue-800: #002eac;
  --color-blue-900: #00207a;
  --color-blue-950: #000b56;
}

SCSS

$blue: #0000ff;
$blue-rgb: 0, 0, 255;
$blue-light: mix(#fff, $blue, 20%);
$blue-dark: mix(#000, $blue, 20%);

.element {
  color: $blue;
  box-shadow: 0 0 0 2px rgba($blue, 0.35);
}