You can set the header text to something like this for non-bold headers:
[tt]My Header[/tt]
As for the gradient - code like this will set the background to white. Replace the RGB values for the color you wanted.
table = event.source.parent.getComponent("Table").viewport.view
table.tableHeader.background = (255,255,255)
Note that this won’t serialize - you’ll have to run this on [tt]internalFrameOpened[/tt] or something.