I think that it will be known as the 5th Gen of iPod Video.
The color screen was just a feature change like the numerous incremental storage boosts, revisions indicate different enclosure.
1st Gen: physical scroll wheel with buttons on the rim
2nd Gen: touch-wheel with buttons on the rim.
3rd Gen: touch sensitive buttons, now lined up between scroll wheel and screen
4th Gen: click-wheel
5th Gen: thinner 'nanolike' enclosure, larger screen, smaller click-wheel