After messing with the codes I figured out how to change the "dark" text input box for custom skins.
Go to: -> AdminCP -> Style Manager -> Edit Template (select custom template) -> CSS Templates and edit "additional.css"
Add the following code to the bottom of additional.css
HTML Code:
.GF3XLO3BES * textarea, .GF3XLO3BES * textbox {
background:#ffffff;
background-color: #ffffff !important;
color: #000000;
border: 1px solid #0c0c0c;
}
.GF3XLO3BAO {
background:#ffffff;
background-color: #ffffff !important;
width: 130px;
}