#639FD9

CSS

:root {
  --blue-bay: #639fd9;
  --blue-bay-rgb: 99 159 217;
  --blue-bay-oklch: oklch(0.685 0.107 248.8);
}

.element {
  color: var(--blue-bay);
  background-color: hsl(209 61% 62%);
  border-color: oklch(0.685 0.107 248.8);
}

Tailwind CSS v4

@theme {
  --color-blue-bay: #639fd9;
  --color-blue-bay-50: #dff8ff;
  --color-blue-bay-100: #ceebff;
  --color-blue-bay-200: #b3d8ff;
  --color-blue-bay-300: #8ebced;
  --color-blue-bay-400: #6ba3db;
  --color-blue-bay-500: #488bc9;
  --color-blue-bay-600: #3e76aa;
  --color-blue-bay-700: #315e88;
  --color-blue-bay-800: #204565;
  --color-blue-bay-900: #153047;
  --color-blue-bay-950: #061c2e;
}

SCSS

$blue-bay: #639fd9;
$blue-bay-rgb: 99, 159, 217;
$blue-bay-light: mix(#fff, $blue-bay, 20%);
$blue-bay-dark: mix(#000, $blue-bay, 20%);

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