You need to edit the .qa-view-count class. Look for that in the qa-styles.css file in your theme. Then add something like "background: #ccc;" to the property list.
Not sure exactly what/how you want to transition but you'd add for example "transition: background 0.5s;" to .qa-view-count and then put a new background on .qa-view-count:hover if you wanted transition on hover.