A "cross" usually means that the geckos are a mix of one line and other geckos, not from that line. A "Blood cross" for example, would mean that the gecko had some Blood Tangerine ancestors and some not. You would have to ask the breeder for details as to how much crossing was done (for example, was the Blood a direct parent, or did the cross happen farther back in the line).
If you breed two crosses, you've essentially just created a mix of all the lines involved on both sides. At that point, it isn't really worth using the line names in the labeling. You would just know that both lines are in the gecko's genetic background.
I some what agree. If I breed a blood tang by a tang I will call it a tang. But say when I breed I w&y to a blood I call the w&y offspring w&y blood cross just so people know the qaulity in the genetics.