Complex sentence: The WM-DD3 was similar in appearance to the WM-DD2 but the buttons had been changed and it was available in the same three colors as the WM-DD and WM-DD2, but it was also available in black.
Split into simpler sentences: The WM-DD3 was similar in appearance to the WM-DD2 but the button layout had been changed. It was available in the same three colors as the WM-DD and WM-DD2, but was also available in black.