How to reproduce:
1. Create a new Unity project
2. In the Project window, right-click -> Create -> Shader Graph -> Any Shader Graph
3. Open the created Shader Graph
4. Change the Color Mode to "User Defined"
5. Create any Node -> right-click on it -> Color -> Change
6. Observe the results

Expected result: Color Picker is opened
Actual results: Color Picker is not opened and the warning is thrown

Reproducible with: 6000.0.56f1, 6000.1.16f1, 6000.2.1f1, 6000.3.0a5

Reproducible on: Ubuntu 24, macOS Sequoia 15.5 (M1)
Not reproducible on: No other environment tested