#3D747E

CSS

:root {
  --mysterious-blue: #3d747e;
  --mysterious-blue-rgb: 61 116 126;
  --mysterious-blue-oklch: oklch(0.525 0.06 210.7);
}

.element {
  color: var(--mysterious-blue);
  background-color: hsl(189 35% 37%);
  border-color: oklch(0.525 0.06 210.7);
}

Tailwind CSS v4

@theme {
  --color-mysterious-blue: #3d747e;
  --color-mysterious-blue-50: #e3faff;
  --color-mysterious-blue-100: #d2eef4;
  --color-mysterious-blue-200: #b8dce4;
  --color-mysterious-blue-300: #94c0ca;
  --color-mysterious-blue-400: #74a9b2;
  --color-mysterious-blue-500: #53919d;
  --color-mysterious-blue-600: #477b84;
  --color-mysterious-blue-700: #39626a;
  --color-mysterious-blue-800: #28484d;
  --color-mysterious-blue-900: #1b3236;
  --color-mysterious-blue-950: #0b1e21;
}

SCSS

$mysterious-blue: #3d747e;
$mysterious-blue-rgb: 61, 116, 126;
$mysterious-blue-light: mix(#fff, $mysterious-blue, 20%);
$mysterious-blue-dark: mix(#000, $mysterious-blue, 20%);

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