Avoiding use of the default shader
If you reference a file in which you’ve altered the default shader (lambert1), these changes are superseded by the default shader of the parent file. To avoid this situation, create a new shader in the child file and assign that rather than using the default shader.
If you reference a file into your current scene with shared shading networks enabled, the shading networks from the referenced scene are combined with those in the current scene (including those of any references). This avoids creating duplicate shading networks when you want the same ones used throughout your scene, including the reference.
Shading networks can only be shared if the shading networks are identical. Maya considers two shading networks to be identical only if all the nodes included in it have both the same name and type while traveling upstream from the shading group.
While the name and type of each node in the shading network must be identical in order for the shading network to be shared, the actual values in each node are not considered. So, a node in a child scene with one value (for example, blue) is considered identical to a node in the parent scene with a different value (for example, red) as long as its name and type match.
However, certain shading networks cannot be shared. They are:
If any of these items appear in the shading network, the network is not shared when the file is referenced with shared shading networks enabled.
Any items that exist downstream of the shading network are also not shared. The only items shared are those items upstream of the shading network.
All edits to referenced nodes that are shared are stored on one common shared reference node. Shared references can only be deleted from the Reference Editor using the Remove Reference menu item. The shared reference node remains for any references that were shared and is only removed when the last shared reference is removed.
Dynamic attributes that are added to a shading network that is subsequently shared may be lost unless the same attributes are created on each of the shading networks to be shared prior to sharing.