While IU's previous album, Chat-Shire, deliberated the confusion and anxieties of a twenty-three year old, Palette offers the perspective of someone at a more mature stage in life. A body of work that tells the story of self-actualization, the album reads similarly to the final chapters of a bildungsroman where the main character embraces adulthood.
As such, Palette can be taken to refer to the various people in life that one comes across, and their different aspects—appreciating them in a celebratory way.
The shooting for the album jacket was an extensive process. IU decided to have her in similar poses and shots were taken to that of her previous album Last Fantasy, to highlight the differences in maturity that have developed.
source: wikipedia