The other 3 groupings are actually clues.
- Yellow is made up of jumbles... things that have been mixed up
- Green is made up for terms for public recognition
- Blue is made up of things you'd find listed on an artworks info card
That leaves us with clues that Purple would be artists of some renown, jumbled up. Quite the clever puzzle
For the less art inclined that would be Salvador DALI, Edgar DEGAS, Claude MONET, and Francisco GOYA