My opponent cast Assemble From Parts on Toxrill, The Corrosive and then created the copy of the creature. The copy couldn't be targeted by Vanishing Verse even though it was only a single color (the original creature is black and the copy was made black as part of Assemble From Parts' ability). Black + black is still just black and should be a valid target. The same problem happening when I tried to target a copy of Cemetery Desecrator. See screenshot.