Steps to reproduce:
1. Open the attached “unitydebug.zip” project
2. Open the “ScenePage.uxml” file in UI Builder from Assets → UI → Templates
3. Select the “#Test” object from the “ScenePage.uss” file
4. Click the three dots near background color
5. Type “--Variable” in the Search bar
6. Observe the Search results

Expected result: Both “--VariableOK” and “--VariableNotOK” are shown as previews
Actual result: Only “--VariableOK” is shown

Reproducible in: 2021.2.0a20, 2021.3.1f1, 2022.3.51f1, 6000.0.26f1, 6000.1.0a3
Not reproducible in: 2021.3.45f1, 2021.2.0a19
Fixed in: 2021.3.2f1

Reproducible on: Windows 11, Windows 10
Not reproducible on: No other environment tested

Note: Manually setting the background color to “--VariableNotOK” sets the background to “--VariableOK”