Make field 'invisible' on form

I have a form where I have an text input field (#input_69) and I want to 'hide' it on the form. I've set the label color to the background color and the field background color to the form color, but for some reason there is still a slight white-ish border around the field.

Any idea what CSS code I can use to completely hide that field? I know I'm missing something...

Any particular reason why you are using CSS codes to hide a field?

You can actually hide a field in the field properties under the advanced tab.