White light backdifracted from a circularly symmetric diffraction grating has coloured the mirror closer to the grating in red and further mirror in blue. The blue light circle can be seen on the red mirror.
<a href="//commons.wikimedia.org/w/index.php?title=User:Ptrr&amp;action=edit&amp;redlink=1" class="new" title="User:Ptrr (page does not exist)">Peeter Piksarv</a>
CC BY-SA 3.0
<span class="int-own-work" lang="en">Own work</span>