I believe you're using the DeveloperExpress control suite.
In your GridBuilder, override BuildCore().
In its implementation, access BindingManager.GridView to get the XtraGridView itself.
After that you're on your own. I don't know much about formatting XtraGrids. Maybe there's something in the Appearance object. Read the DevEx documentation and if you figure it out, post it here so the rest of us will know.