#3F6F9F

CSS

:root {
  --naval: #3f6f9f;
  --naval-rgb: 63 111 159;
  --naval-oklch: oklch(0.529 0.092 250);
}

.element {
  color: var(--naval);
  background-color: hsl(210 43% 44%);
  border-color: oklch(0.529 0.092 250);
}

Tailwind CSS v4

@theme {
  --color-naval: #3f6f9f;
  --color-naval-50: #e3f8ff;
  --color-naval-100: #d2ebff;
  --color-naval-200: #b8d8fb;
  --color-naval-300: #95bbe6;
  --color-naval-400: #74a3d3;
  --color-naval-500: #548ac1;
  --color-naval-600: #4875a3;
  --color-naval-700: #395e83;
  --color-naval-800: #274561;
  --color-naval-900: #1a3044;
  --color-naval-950: #0a1c2c;
}

SCSS

$naval: #3f6f9f;
$naval-rgb: 63, 111, 159;
$naval-light: mix(#fff, $naval, 20%);
$naval-dark: mix(#000, $naval, 20%);

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