Modify the D3D demos to color +Z dark blue and -Z light blue

[russell-taylor]

The D3D demos all have their cube worlds colored with +Z light blue and -Z dark blue. This is the opposite of the coloration for the OpenGL demos.

This makes the demos look the same with the two interfaces, but they should not -- the Direct3D demos are using a left-handed world coordinate system. Need to switch all of the D3D ones to the same color convention.