Jim -- I plead guilty to having fun playing with colors on the inside of blanks -- especially with Lucite blanks. There are opportunities to lightly scuff the 1st coat of paint and add a complementary/contracting color for different effects. The same blank can have radically different appearance depending on the colors used. The scuffing gave me an aha as to the weakness of the paint-blank bond.
Craft paints work reasonably well but do not bond well to the plastics, especially if the inside of the blanks is polished (as in Lucite) - and that results in a mediocre glue bond because while the glue bonds to the paint, the paint-blank bond is weak. -- It works but needs a light hand turning.
Testors bond is a bit better, but take care.
Silver is my fall back color selection -- and is easy to find in a spray primer and spray primers are better bonding to the plastics.
If you want to test the bonding -- use the outside of the blank and paint a bit even put a bit of glue on it and see how firm the bond of paint to blank is.