Warnings “Assets/ColorBugStyleSheet.uss (line 5): Expected (<color>) but found 'rgba(255, 255, 255, .85)' -unity-text-outline-color: rgba(255, 255, 255, .85) -> Unsupported color

Reproduction steps:
1. Create a new project
2. Import “Repro.uss“
3. Observe the Console

Expected result: No Warnings exist
Actual result: Warnings “Assets/ColorBugStyleSheet.uss (line 5): warning: Expected (<color>) but found 'rgba(255, 255, 255, .85)'
-unity-text-outline-color: rgba(255, 255, 255, .85) -> Unsupported color 'rgba(255, 255, 255, .85)'.“ are present

Reproducible with: 6000.3.0a2 (d454866889d5), 6000.3.3f1, 6000.4.0b3, 6000.5.0a4
Not reproducible on: 6000.0.65f1, 6000.3.0a1 (4592b02ab560)

Testing environment: Windows 10 Enterprise 21H2
Not reproducible on: No other environment tested