#517A9F

CSS

:root {
  --into-the-blue: #517a9f;
  --into-the-blue-rgb: 81 122 159;
  --into-the-blue-oklch: oklch(0.565 0.074 246.7);
}

.element {
  color: var(--into-the-blue);
  background-color: hsl(208 33% 47%);
  border-color: oklch(0.565 0.074 246.7);
}

Tailwind CSS v4

@theme {
  --color-into-the-blue: #517a9f;
  --color-into-the-blue-50: #e6f8ff;
  --color-into-the-blue-100: #d6ebff;
  --color-into-the-blue-200: #bdd8f3;
  --color-into-the-blue-300: #9bbbdc;
  --color-into-the-blue-400: #7ba3c8;
  --color-into-the-blue-500: #5d8bb5;
  --color-into-the-blue-600: #4f7698;
  --color-into-the-blue-700: #3f5e7a;
  --color-into-the-blue-800: #2c455a;
  --color-into-the-blue-900: #1e303f;
  --color-into-the-blue-950: #0d1c28;
}

SCSS

$into-the-blue: #517a9f;
$into-the-blue-rgb: 81, 122, 159;
$into-the-blue-light: mix(#fff, $into-the-blue, 20%);
$into-the-blue-dark: mix(#000, $into-the-blue, 20%);

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