Spotted in our nightly test run a couple times over the last few days:

IconifyTest > canIconifyDecoratedStage FAILED
    junit.framework.AssertionFailedError: expected:rgba(255,0,0,255) but was:rgba(189,189,189,255)
        at test.robot.testharness.VisualTestBase.assertColorEquals(VisualTestBase.java:173)
        at test.robot.javafx.stage.IconifyTest.lambda$canIconifyStage$4(IconifyTest.java:99)