text fields can't change background color

In style.css this code is present:

/*********/
/* FORMS */
/*********/

form {
  margin: 0;
  padding: 0;
}

select.form-select,
input.form-text,
textarea.form-textarea {                                      /* default styling for all text fields */
  background: #F6F9FB url('images/form-bg.png') left top;
  color: #666666; 
  border: 1px solid #9BABB0;
  padding: 2px 0;
  -moz-border-radius: 4px;
  -webkit-border-radius: 4px;
}

The image in the background of text fields prevents the posibility to change its color. For that reason fields like those ones binded with farbtastic color picker will not work (example garland config page).

I looked to that png used as background an at least for me is an almost unnoticeable gradient.

If that png is dropped the text fields background color will be changeable. It could be done just changing that background line in style.css to:

  background: #F6F9FB;