I offer a few interpretations:

Platonic: The ideal form of "paint" is applied to the ideal form of a "wall," yet the individual instantiations of those forms in reality only exhibit the specific qualities particular to themselves. The form of "paint" contains both the specific qualities of "pretty" and "not pretty."

Taoist: Paint and wall are part of the 10,000 things. The 10,000 things are the Tao. The Tao is not the 10,000 things.

Christian: The paint adheres to the wall by the grace of God and the sacrifice of his son, Jesus Christ.

Kantian: The quality of color is inherent in the noumenal world of the paint. The physical phenomenon of putting the paint on the wall is a result of our limited perception of all noumena by way of space and time. The paint goes on the wall only in our limited perception.

Liberation Theological: We should embrace and accept the pretty colors and the ugly colors, for they were all made by God. Jesus' sacrifice has freed us from the social condemnations of "ugly colors."

Existentialist: Absent the "gods" of our forefathers, we are left to choose why we would paint, or not paint, the wall.

Oprah-ist: If you make a vision-collage and really believe there is paint on the wall the universe will vibrate hard enough to attract your painted wall. That's how Henry Ford invented the car. If it doesn't happen, it's your fault for "wanting" instead of "believing."

Nietzschean: Paint is a flat circle.