It's been well stablished that you cannot change every detail on browser generated controls. For example the color of the arrow on a select dropdown, or the dot of a radio, etc...
You can create your custom controls, use some library like JQuery UI, or.... maybe play around a little with css.
Here's an experiment to fake a colored dot on a radio, using :before pseudo element:
http://jsfiddle.net/bvtngh57/
input[type="radio"]:checked:before {
content: "";
display: block;
position: relative;
top: 3px;
left: 3px;
width: 6px;
height: 6px;
border-radius: 50%;
background: red;
}
Result:
