#639DE5

CSS

:root {
  --blue-bay: #639de5;
  --blue-bay-rgb: 99 157 229;
  --blue-bay-oklch: oklch(0.687 0.123 254.6);
}

.element {
  color: var(--blue-bay);
  background-color: hsl(213 71% 64%);
  border-color: oklch(0.687 0.123 254.6);
}

Tailwind CSS v4

@theme {
  --color-blue-bay: #639de5;
  --color-blue-bay-50: #dff7ff;
  --color-blue-bay-100: #ceeaff;
  --color-blue-bay-200: #b3d7ff;
  --color-blue-bay-300: #8ebaf6;
  --color-blue-bay-400: #6aa1e6;
  --color-blue-bay-500: #4888d6;
  --color-blue-bay-600: #3e73b4;
  --color-blue-bay-700: #315c91;
  --color-blue-bay-800: #20446c;
  --color-blue-bay-900: #152f4c;
  --color-blue-bay-950: #061b32;
}

SCSS

$blue-bay: #639de5;
$blue-bay-rgb: 99, 157, 229;
$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);
}