Seen on Windows 7 at 120 dpi,
I think this is an unstable test since it I can't find anything that changed
java.lang.RuntimeException: Expected java.awt.Color[r=255,g=0,b=0] got java.awt.Color[r=239,g=214,b=214]
at SiblingChildOrderTest.main(SiblingChildOrderTest.java:70)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at com.sun.javatest.regtest.agent.MainWrapper$MainThread.run(MainWrapper.java:115)
at java.base/java.lang.Thread.run(Thread.java:844)

JavaTest Message: Test threw exception: java.lang.RuntimeException: Expected java.awt.Color[r=255,g=0,b=0] got java.awt.Color[r=239,g=214,b=214]
JavaTest Message: shutting down test

STATUS:Failed.`main' threw exception: java.lang.RuntimeException: Expected java.awt.Color[r=255,g=0,b=0] got java.awt.Color[r=244,g=0,b=0]
JavaTest Message: shutting down test

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It was also reported on MacOS but that was an environment issue.