#367BA5

CSS

:root {
  --zenith: #367ba5;
  --zenith-rgb: 54 123 165;
  --zenith-oklch: oklch(0.557 0.095 238.5);
}

.element {
  color: var(--zenith);
  background-color: hsl(203 51% 43%);
  border-color: oklch(0.557 0.095 238.5);
}

Tailwind CSS v4

@theme {
  --color-zenith: #367ba5;
  --color-zenith-50: #def9ff;
  --color-zenith-100: #ccedff;
  --color-zenith-200: #b0dafa;
  --color-zenith-300: #8bbee4;
  --color-zenith-400: #66a7d0;
  --color-zenith-500: #418ebe;
  --color-zenith-600: #3879a0;
  --color-zenith-700: #2d6181;
  --color-zenith-800: #1d475f;
  --color-zenith-900: #133143;
  --color-zenith-950: #051d2b;
}

SCSS

$zenith: #367ba5;
$zenith-rgb: 54, 123, 165;
$zenith-light: mix(#fff, $zenith, 20%);
$zenith-dark: mix(#000, $zenith, 20%);

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