JSBIN DEMO
Is this some kind of bug or they just made it wrong?
Shouldn't the dark gray be DARKER then the default grey?
HTML
<div class="lightgrey">Light Grey</div>
<div class="grey">Grey</div>
<div class="darkgrey">Dark Grey</div>
CSS
.lightgrey {background: lightgrey}
.grey {background: grey}
.darkgrey {background: darkgrey}