<p>I'm talking about this puppy:</p>

<p><a href="https://i.stack.imgur.com/qzm27.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/qzm27.png" alt="CrossValidated logo"></a></p>

<p>It kinda looks like a heat-map or correlogram, but I would expect the other diagonal to be picked out in green, were that the case. (My expectations may be flawed. :)</p>

<p>I read the <a href="https://stats.meta.stackexchange.com/questions/269/what-should-our-logo-and-site-design-look-like/459#459">post by the logo's seeming designer</a>, but that doesn't explain. </p>

<p>What kind of graph is it?</p>
