#5B9FE4

CSS

:root {
  --blue-bay: #5b9fe4;
  --blue-bay-rgb: 91 159 228;
  --blue-bay-oklch: oklch(0.687 0.124 250.4);
}

.element {
  color: var(--blue-bay);
  background-color: hsl(210 72% 63%);
  border-color: oklch(0.687 0.124 250.4);
}

Tailwind CSS v4

@theme {
  --color-blue-bay: #5b9fe4;
  --color-blue-bay-50: #ddf8ff;
  --color-blue-bay-100: #cbebff;
  --color-blue-bay-200: #afd8ff;
  --color-blue-bay-300: #89bbf5;
  --color-blue-bay-400: #63a3e5;
  --color-blue-bay-500: #3d8ad4;
  --color-blue-bay-600: #3575b3;
  --color-blue-bay-700: #2a5d90;
  --color-blue-bay-800: #1a456b;
  --color-blue-bay-900: #11304b;
  --color-blue-bay-950: #041c32;
}

SCSS

$blue-bay: #5b9fe4;
$blue-bay-rgb: 91, 159, 228;
$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);
}