JTextPane and his ancestors JEditorPane and JTextComponent won't respect the color defined with setBackground(Color) since they display a "styled document" and expect the background color to be defined in the content. You'll always see a white background.

To change the background color (without modifying the content) you have to define attributes for the document:

Today I wanted to embed a SWT component (Browser) into an existing JFrame. This is the way it works: