#91CFE4

CSS

:root {
  --over-the-sky: #91cfe4;
  --over-the-sky-rgb: 145 207 228;
  --over-the-sky-oklch: oklch(0.82 0.07 221);
}

.element {
  color: var(--over-the-sky);
  background-color: hsl(195 61% 73%);
  border-color: oklch(0.82 0.07 221);
}

Tailwind CSS v4

@theme {
  --color-over-the-sky: #91cfe4;
  --color-over-the-sky-50: #e1faff;
  --color-over-the-sky-100: #d0eef9;
  --color-over-the-sky-200: #b5dbea;
  --color-over-the-sky-300: #91c0d2;
  --color-over-the-sky-400: #6fa8bc;
  --color-over-the-sky-500: #4c91a7;
  --color-over-the-sky-600: #427b8d;
  --color-over-the-sky-700: #346271;
  --color-over-the-sky-800: #244853;
  --color-over-the-sky-900: #18323a;
  --color-over-the-sky-950: #081e24;
}

SCSS

$over-the-sky: #91cfe4;
$over-the-sky-rgb: 145, 207, 228;
$over-the-sky-light: mix(#fff, $over-the-sky, 20%);
$over-the-sky-dark: mix(#000, $over-the-sky, 20%);

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