#00437B

CSS

:root {
  --mermaid-blues: #00437b;
  --mermaid-blues-rgb: 0 67 123;
  --mermaid-blues-oklch: oklch(0.38 0.112 251.5);
}

.element {
  color: var(--mermaid-blues);
  background-color: hsl(207 100% 24%);
  border-color: oklch(0.38 0.112 251.5);
}

Tailwind CSS v4

@theme {
  --color-mermaid-blues: #00437b;
  --color-mermaid-blues-50: #dff8ff;
  --color-mermaid-blues-100: #ceebff;
  --color-mermaid-blues-200: #b3d8ff;
  --color-mermaid-blues-300: #8fbbf0;
  --color-mermaid-blues-400: #6ba3df;
  --color-mermaid-blues-500: #498ace;
  --color-mermaid-blues-600: #3f75ad;
  --color-mermaid-blues-700: #325d8b;
  --color-mermaid-blues-800: #214567;
  --color-mermaid-blues-900: #163049;
  --color-mermaid-blues-950: #071c30;
}

SCSS

$mermaid-blues: #00437b;
$mermaid-blues-rgb: 0, 67, 123;
$mermaid-blues-light: mix(#fff, $mermaid-blues, 20%);
$mermaid-blues-dark: mix(#000, $mermaid-blues, 20%);

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