A seven-vertex odd cycle and its complement, showing in both cases an optimal coloring of the graph and a maximum clique. Since neither of the graphs uses a number of colors equal to its clique size, they are not <a href="https://en.wikipedia.org/wiki/Perfect_graph" class="extiw" title="en:Perfect graph">perfect graphs</a>.
<a href="//commons.wikimedia.org/wiki/User:David_Eppstein" class="mw-redirect" title="User:David Eppstein">David Eppstein</a>
<span class="int-own-work" lang="en">Own work</span>