Please help with blending

I try to draw blending plane witch cut cube of lines.
Here is the picture:

As you see problem is that lines which should be blue is mixed with red blending plane and lines which should be mixed is blue.

Please help…

It is mostly probably correct, however the orientation is not like what you think (hard to tell with ortho view, try with perspective).
Current view looks like we look up toward a cube above.