Hi,
You can only pass CSS class name to overrideStyle. You can not pass inline styles. So for example, you would use it like this:
    
        Code: CSS
        
        .blue_text
{
    color: blue;
} 
     
 
    
        Code: JavaScript
        
        gridItem.getCell(7).overrideStyle("blue_text"); 
     
 
Note here "blue_text" is a CSS class name that you have already defined in your page.
Thanks!