#517AA3

CSS

:root {
  --into-the-blue: #517aa3;
  --into-the-blue-rgb: 81 122 163;
  --into-the-blue-oklch: oklch(0.567 0.079 249.4);
}

.element {
  color: var(--into-the-blue);
  background-color: hsl(210 34% 48%);
  border-color: oklch(0.567 0.079 249.4);
}

Tailwind CSS v4

@theme {
  --color-into-the-blue: #517aa3;
  --color-into-the-blue-50: #e5f7ff;
  --color-into-the-blue-100: #d5eaff;
  --color-into-the-blue-200: #bcd7f6;
  --color-into-the-blue-300: #9abbdf;
  --color-into-the-blue-400: #7aa3cb;
  --color-into-the-blue-500: #5c8ab8;
  --color-into-the-blue-600: #4e759c;
  --color-into-the-blue-700: #3e5e7d;
  --color-into-the-blue-800: #2b455c;
  --color-into-the-blue-900: #1d3041;
  --color-into-the-blue-950: #0d1c29;
}

SCSS

$into-the-blue: #517aa3;
$into-the-blue-rgb: 81, 122, 163;
$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);
}