Graph Toolkit's Placemat color is not applied correctly when changed right after creating the Placemat

How to reproduce:
1. Create a new Unity project and import the "MySimpleGraph" Script
2. In the Project window, right-click -> Create -> Graph Toolkit Samples -> Simple Graph -> Open the Graph
3. In the Canvas, right-click -> Create Placemat
4. Without clicking anything else, in the Graph Inspector, change the color and observe the results
5. Unfocus the Placemat and observe the results

Expected results: The color doesn't change when the Placemat is unselected
Actual results: The color changes when the Placemat is unselected

Reproducible with: 6000.4.0b7, 6000.5.0a6

Reproducible on: macOS Tahoe 26 (M1)
Not reproducible on: No other environment tested

Note: Reproducible only if the Placemat wasn't unfocused after creation