I disagree on Vermont. The other two are clear cut ; there was no dispute as to whether they were part of Massachussetts/Virginia prior to achieving statehood, and especially at the time their respective states formally joined the union.
Vermont, on the other hand, had declared formal independance from New York in 1777, ie, before NY ever formally ratified the constitution. While this does not make them an independant nation (as others have claimed), it certainly means (since that independance from NY was eventually recognized de jure when Vermont was allowed to sign the constitution as a full state) that simply saying "they were part of the thirteen revolted colonies as a part of New York" is not really accurate either. Maybe very briefly (ie, 1776-1777), but...
Personally, if I had to do the homework, I would use three colors : one for the present thirteen states corresponding (by name) to the thirteen colonies ; another for the two states that were split off from the original thirteen in the 19th century (WV and Maine), and the final one for Vermont, with a note explaining that Vermont declared independence from New York very early in the revolution, but that the other states (mostly New York) took several years to acknowledge that fact.