Bruce Levison (designer of the Odd'l Rockets Corkscrew) made two of my carded BT-20 models, the Patriot and A-20 Demon. He kept track of the builds and passed on a tip for body tube skins.
"Use a white length of BT-20 if available, or coat a brown cardboard tube with white paint or primer. The dark color of the tube will show through the 24lb paper to some extent the white tube makes the colors look brighter."
I hadn't noticed and brown tube showing through the white paper skin overlay. I guess I've used white BT-5 and BT-20 tubes when makking carded down scales. Bruce's tip makes sense, a brown tube color might show through making a lighter print skin darker.
TIP: Be sure to use a white body tube (or painted white) when making carded models with printed wraps.