The CSS Reference Guide (http://docs.oracle.com/javase/8/javafx/api/javafx/scene/doc-files/cssref.html#tabpane) says that the following hierarchy is valid:

{code}
tab — Tab
   tab-label — Label
   tab-close-button — StackPane
{code}

Actually this is wrong. A short test using 8u40 provides the following result:

.tab > .tab-label ==> Does not affect the header label.
.tab > * > .tab-label ==> Affects the header label.

Hence the guide is wrong as apparently some intermediate class is missing in the outline of .tab content. this is very confusing and unexpected.