To Toggle Material Display
The stock is displayed in green, to make it easily distinguishable from the reference part geometry, which is displayed in the default Geometry system color (usually, white).
By default, the stock model is displayed in its current machined state; that is, it is shown as the entire model, less any material that has been removed by a tool path.
Another option for stock display is to show it as it would exist if all currently defined machining features were completely machined. This way, you can easily view the material that is left to be machined off, and create appropriate machining features.
To toggle between the two ways of viewing the stock material:
1. Click > 
Material Removal Display.
Material Removal Display.The system displays the stock in such a way that only the "extra" material left to be machined off is shown in green. The system temporarily removes from the stock model all the material corresponding to the currently defined features. Whenever the edges of the stock coincide with the edges of the reference model, they are shown in Geometry color.
2. To toggle back to the all-green stock display, click Material Removal Display once more.
Material Removal Display once more.