Null JS provides pre-defined classes to color background:

Note that some of the backgrounds require the use of white text in order to improve visibility.

<div class="null-background-pink">Pink Background</div>

<div class="null-background-green">Green Background</div>

<div class="null-background-blue">Blue Background</div>

<div class="null-background-purple">Purple Background</div>

<div class="null-background-yellow">Yellow Background</div>

<div class="null-background-brown">Brown Background</div>

<div class="null-background-grey">Grey Background</div>

<div class="null-background-orange">Orange Background</div>

<div class="null-background-red">Red Background</div>

<div class="null-background-white">White Background</div>

<div class="null-background-light-grey">Main Background</div>

<div class="null-background-main">Main Background</div>