1. Create the shape for button.

2. Select Interactive Fill Tool from toolbox and drag the cursor from top left to bottom right corner. Change the colors from the property bar.

3. Select Pick Tool.

Select the shape.

Press Shift and drag the shape little inside from any corner point. Without releasing left mouse button click right mouse button.

You will get the offset copy of the original shape exactly at the center.

4. Select the second copy which is inside.

5. Select Interactive Fill Tool

6. Turn the mark of the tool (dotted line with small black & white rectangles) in opposite direction. It should look as if it is dragged from Bottom right to upper left corner.

7. Double click the pick tool so that both the shapes will get selected simultaneously.

8. Right click on the cross mark at the top of the color palette. The out line will disappear.

9. Create the following buttons with similar method.