How to make my prefixes look like this?

[vijayninel]

you will have to put something like this in the Title (Rich Text) field:

<span style="background: none repeat scroll 0% 0% rgb(255, 105, 0);" class="prefix">Overclocking</span>

Then in your Admin CP go to style manager > style > all style options and in the additional CSS definitions box at the end put

.prefix {
color:#ffffff;
font-size: 0.85em;
font-weight: normal;
padding: 3px 10px;
text-align: center;
}

Change the values as needed.