Cheryl,
Increasing the blue center strip will make the diamonds smaller and this will result in more space between the diamonds. However, it is likely to make the small diamond in the center disappear. If this happens and you still want that small diamond, go back to the Laminate Wizard and make the white (holly?) strip narrower. While you do this, experiment with changing the width of the first and last strip and see how that changes the overall size of the diamond.
This is all trial and error. You can change the shape of the diamond by changing the angle and this will cause the width of the diamonds to shrink or expand. If you want the diamond to be square, leave the angle at 45 degrees and adjusting the blue center strip will make the diamond larger or smaller but the width of the strips and the repeating unit will only change if you change the First Cut Width.
Experiment with changing these things and you'll see what happens when you change the various parameters. You will soon be able to dial in the exact results you're after.