Steps to reproduce:
1. Open the attached “IN-134952_MaterialBug.zip” project
2. Open the “Document.uxml” asset in the Project window
3. Pick any element in the UI Builder Hierarchy
4. In the UI Builder Inspector, go to the “Material” tab
5. Change the material from TestMaterial to None or vice versa
6. Observe the UI Builder

Actual Result: The image is darker when using a test shader
Expected Result: There is no difference between the test shader and no material

Reproducible with: 6000.3.0a5 (f9a1fab5607a), 6000.3.10f1, 6000.4.0b10, 6000.5.0a7
Not reproducible with: 6000.0.68f1, 6000.3.0a4 (No material option for VisualElements in UI Builder)

Reproducible on: MacOS Sequoia 15.7.3 (M1 Max)
Not reproducible on: No other environments tested

Note: The VisualElements are not rendered darker when they are rendered in the scene, this only applies to UI Builder