This two-stage activity culminates in the creation of a collaborative worksheet containing questions that students make themselves for their peers to complete. It offers good solid practice in identifying and using different forms of colour adjectives in French, in a fun context.
Writing their own sentences will allow students to focus on proper sentence structure, and also encourage creativity and perhaps a little silliness, as they create images for their classmates to colour.
This activity is intended for use after students have been introduced to the concept of adjective agreement, and are familiar with its basic forms. An introduction to this content is provided in another one of my resources called "Hallowe'en Adjective Agreement Introduction".