If you use Firefox > Menu > Web Developer and then either Page Source or Inspector you can find the html element that holds it. See image using Inspector.
You can then add to a file /media/yourblogname/style.css appropriate code.

You can see the <div class="evo_post_head"

So place an entry like

div.evo_post_head{color:blue} in the mentioned css file

This color overide would affect any other info you may chose to place in that div

You can see, to the right of the image below that the property and color (999) are set in style.css which is likely to be in the skin folder.

Alternatively you can look at the css file in you skin, where the color may be set and just change it there.

6.10.3 [/skins/asevo/style.css]

.evo_post_head {
	font-size: 76%;
	color: #999;
}

Many thanks again amoun, that's sorted it.