How to reproduce:
1. Open the user's attached to project "case_1306190-UIToolkit-PropertyField-RightClick.zip"
2. Select "GameObject" Prefab in the Project window
3. In the Inspector window, find the "Monobehaviour IMGUI (Script)" component
4. Click on "That Struct" > "Color" field and notice that the "Color" property label is not changed
5. Close Color Picker window
6. In the Inspector window, find the "Monobehaviour UI Toolkit (Script)" component
7. Click on "That Struct" > "Color" field
8. Leave the Color Picker window open
9. Observe the "Color" property's label

Expected result: The Color property label is not changed when the Color Picker window is open. UI Toolkit and IMGUI behave the same way
Actual result: The Color property label is highlighted when the Color Picker window is open. UI Toolkit and IMGUI behave differently

Reproducible with: 2020.2.0a12 (built-in UI Toolkit), 2020.2.2f1 (built-in UI Toolkit, UI Toolkit 1.0.0-preview.13), 2021.1.0b6, 2021.2.0a4 (built-in UI Toolkit)
Not reproducible with: 2019.4.20f1, 2020.2.0a11 (built-in UI Toolkit)
Could not test with: 2018.4.31f1 (built-in UI Toolkit) (due to errors), 2019.4.20f1 (UI Toolkit package is not introduced yet), 2020.2.0a11, 2020.2.0a12, 2021.1.0b6, 2021.2.0a4 (UI Toolkit 1.0.0-preview.13) (due to errors)

Notes:
- Up to 2020.2.0a11 version, UI Toolkit's Color property behaves the same as IMGUI's Color property. UI Toolkit's and IMGUI's Color property label is highlighted after opening the Color Picker window