“ I'm almost finished painting. But it's missing something.
Of course! Something blue, but the Blue Fruit is all gone.
More Blue for the Picture! (絵に足りない青色！, E ni Tarinai Aoiro!, lit. Not Enough Blue Color for the Painting!) is an event is Tomba! 2: The Evil Swine Return.
Get the painter some blue paint.
Enter the hut in the middle of Donglin Forest and talk to the painter to activate the event.
The blue paint can be found in the form of a fruit in the upper area of this forest section. Swing onto it to grab it, and return to the artist. Speak to him to complete the event and receive the Blue Key.