JSFiddle - React, Tailwind, and code Playground

HTML

<div id="maincontentcontainer">
		<div id="maincontent">
			<div class="section group">
				<div class="col" id="callout1" style="background-color: #00B300">
					Background should be green
				</div>
				<div class="col" id="callout2" style="background-color: #00CC00">
					Background should be lighter green
				</div>
				<div class="col span_1_of_3" id="callout3" style="background-color: #00E600;">
					Background should be lighter green
				</div>
			</div>
		</div>
	</div>

CSS

#maincontent .col {
		background: #ccc;
		background: rgba(204, 204, 204, 0.85);
	}

   #callout1	{		
		text-align:center;
    margin-bottom: 10px;
	}
	#callout2	{	
		text-align:center;
    margin-bottom: 10px;
	}
     #callout3	{	
		text-align:center;
    margin-bottom: 10px;
	}