#4C78A3

CSS

:root {
  --into-the-blue: #4c78a3;
  --into-the-blue-rgb: 76 120 163;
  --into-the-blue-oklch: oklch(0.559 0.083 249);
}

.element {
  color: var(--into-the-blue);
  background-color: hsl(210 36% 47%);
  border-color: oklch(0.559 0.083 249);
}

Tailwind CSS v4

@theme {
  --color-into-the-blue: #4c78a3;
  --color-into-the-blue-50: #e4f8ff;
  --color-into-the-blue-100: #d4ebff;
  --color-into-the-blue-200: #bbd8f7;
  --color-into-the-blue-300: #98bbe1;
  --color-into-the-blue-400: #78a3ce;
  --color-into-the-blue-500: #598abb;
  --color-into-the-blue-600: #4c759e;
  --color-into-the-blue-700: #3c5e7f;
  --color-into-the-blue-800: #2a455e;
  --color-into-the-blue-900: #1c3042;
  --color-into-the-blue-950: #0c1c2a;
}

SCSS

$into-the-blue: #4c78a3;
$into-the-blue-rgb: 76, 120, 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);
}