The Colour of Revenge (Inkheart book #4), Cornelia Funke

After five happy years, Meggie, her father Mo and the fire-eater Dustfinger, along with a host of new friends, feel safe and settled. But arch-villain Orpheus has found an unexpected way to wreak his revenge on the Inkworld! He has corrupted an artist to create bewitched portraits that will see the heroes fade to grey – Dustfinger, his brave stepson, Jehan, and his enigmatic friend Lilia, must come together to find a way to save them all! This is the Colour of Revenge . . .