c.contrast

 r.repetition

 a.alignment

 p.proximity

for contrast the purple and yellowish orange are on the opposite sides of the colour wheel and i believe they complement each other.

second the repetition in this poster are the word of the the poster that have the same color to it.

also the alignment of the title is not scattered but properly placed.

last in proximity the poster has an organized setting between the light and the child to make the lighting look as such a swing.