#00419A

CSS

:root {
  --cascade-twilight: #00419a;
  --cascade-twilight-rgb: 0 65 154;
  --cascade-twilight-oklch: oklch(0.401 0.157 259.2);
}

.element {
  color: var(--cascade-twilight);
  background-color: hsl(215 100% 30%);
  border-color: oklch(0.401 0.157 259.2);
}

Tailwind CSS v4

@theme {
  --color-cascade-twilight: #00419a;
  --color-cascade-twilight-50: #dcf6ff;
  --color-cascade-twilight-100: #cbe9ff;
  --color-cascade-twilight-200: #afd5ff;
  --color-cascade-twilight-300: #8ab7ff;
  --color-cascade-twilight-400: #649efa;
  --color-cascade-twilight-500: #4083ec;
  --color-cascade-twilight-600: #376fc7;
  --color-cascade-twilight-700: #2c59a0;
  --color-cascade-twilight-800: #1a4277;
  --color-cascade-twilight-900: #112d54;
  --color-cascade-twilight-950: #041a39;
}

SCSS

$cascade-twilight: #00419a;
$cascade-twilight-rgb: 0, 65, 154;
$cascade-twilight-light: mix(#fff, $cascade-twilight, 20%);
$cascade-twilight-dark: mix(#000, $cascade-twilight, 20%);

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