Open global.css stylesheet and find;
div.error {
padding: 5px 10px;
border-top: 2px solid #FFD324;
border-bottom: 2px solid #FFD324;
background: #FFF6BF;
font-size: 12px;
}
and change background: #FFF6BF; hex code what ever color you want to use.

Oh! I forgot

Here's a fix;
Within the same global.css , find;
input.textbox {
background: #ffffff;
color: #000000;
border: 1px solid #0f5c8e;
padding: 1px;
}
And change background color.
