How to reproduce:
1. Create a new Unity URP project
2. Create a UI Shader Graph
3. Import the attached “Default_solid_b” shader
4. Open the shader
5. Observe the Preview and Combine Nodes
Actual result: The preview of the Preview Node in which the channel B goes into is displayed half white and half black, and the Combine Node's preview is half white and half yellow
Expected result: The preview of the Preview Node in which the channel B goes into is displayed fully white, and the Combine Node's preview is fully white
Reproducible with: 6000.3.0b6, 6000.3.2f1, 6000.4.0b2, 6000.5.0a3
Could not test with: 2022.69.f1, 2023.1.0a1, 6000.0.64f1 (UITK ShaderGraph was introduced in Unity 6000.3.0b6)
Reproducible on: Windows 11
Not reproducible on: No other environments tested