how can I insert two green slice nodes in a slicer layout manager?
By “green” do you mean you want the view to be called green, color the border green, or use the coronal default orientation?
You can change the color of slice nodes to green for multiple views.
Slice names and labels are unique, so you can only have one of them be “G” / “Green”.
If you mean that you want to show multiple coronal views, then set its orientation by calling sliceNode.SetOrientation (see example). You can set default orientation in the orientation property of your layout (see example of how to create custom layout here).
Actually I want 4 slice nodes.A set of (green, red, yellow) slice nodes and a seperate slice node.Because I had already used the three nodes earlier, how can I create a new sliceNode.
You can create your custom layout, with as many viewers you need, using any default orientations. See example in script repository: https://www.slicer.org/wiki/Documentation/Nightly/ScriptRepository#Customize_viewer_layout