Whatever styling name you have used to STYLE your text boxes...
You just duplicate the style then add :Hover to its name and modify the style
Lets say its called MyTextStyle
Then in your stylsheet it may appear as below...
The style below gives you white background and red text
.MyTextStyle
{
Color: #FF0000;
Background-color: #FFFFFF;
}
The style below gives you Black background and white text
.MyTextStyle:Hover
{
Color: #FFFFFF;
Background-color: #0000;
}
This is probably the BEST way to do it