This graph shows the proportion of the surface that is being used by the main colours of national flags.
Christoph Bartneck and Adrian Clark
CC BY-SA 3.0
<a rel="nofollow" class="external free" href="https://onlinelibrary.wiley.com/doi/full/10.1002/col.21853">https://onlinelibrary.wiley.com/doi/full/10.1002/col.21853</a>