Wordress removing light yellow AdSencse placeholder background (or change it to any other color)

I added some AdSense placeholders to my we page and I like it but the light yellow place holders are a bit annoying. It is really easy to remove or change.

In WordPress log in as an administrator and select Appearance -> Editor

Then open style.css and find ins entry. It might look like

ins {
background: #ffff90;
text-decoration: none;
}

Just change the background value to #ffffff if you want it white. Alternatively, you can remove background line all together.