#00456B

CSS

:root {
  --mermaid-blues: #00456b;
  --mermaid-blues-rgb: 0 69 107;
  --mermaid-blues-oklch: oklch(0.374 0.088 241.8);
}

.element {
  color: var(--mermaid-blues);
  background-color: hsl(201 100% 21%);
  border-color: oklch(0.374 0.088 241.8);
}

Tailwind CSS v4

@theme {
  --color-mermaid-blues: #00456b;
  --color-mermaid-blues-50: #e1f9ff;
  --color-mermaid-blues-100: #d0ecff;
  --color-mermaid-blues-200: #b5d9f8;
  --color-mermaid-blues-300: #91bde2;
  --color-mermaid-blues-400: #6ea5ce;
  --color-mermaid-blues-500: #4c8dbc;
  --color-mermaid-blues-600: #41779e;
  --color-mermaid-blues-700: #34607f;
  --color-mermaid-blues-800: #23465e;
  --color-mermaid-blues-900: #173142;
  --color-mermaid-blues-950: #081d2a;
}

SCSS

$mermaid-blues: #00456b;
$mermaid-blues-rgb: 0, 69, 107;
$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);
}