Could you tell me, what is the class of this table like widget
It's eclipse->window->preferences->java->build path->classpath variables? or if you know how to get it's preference page class
That page is org.eclipse.jdt.internal.ui.preferences.ClasspathVariablesPreferencePage
The actual class path list is a TableViewer
using a label provider that implements IColorProvider
(at least it was, the coloring has been dropped in Eclipse Neon).