Hi,
There is one significant lighting change in the newer version that you should be aware of. In the old version the default lighting was pointed in a fixed direction. In the newer version the default light is fixed to the head, so it is always pointing in the direction of the view. Since transparent textures are modulated, the color depends on the angle at which the light is hitting it, hence the change in color at the different viewing angles. If you want the grate to always be the same color simply disable lighting on it.
Code:
grate = viz.add('grate.wrl')
grate.disable(viz.LIGHTING)
In the code above I'm assuming
grate is the name of your grate object. Hope this helps