I gathered a variety of supplies I had on hand, but curated and presented only the rainbow colors. From top left to bottom right: Thin markers, colored pencils, colored pens (Staedler triplus roller from RSVP), crayons, artist chalk, gel sticks, rainbow tape (RSVP stocks lots of fun washi tape as well), watercolors and rainbow stickers. Mine are just crayola paints, but these are the high quality paints we have at preschool. Including a few links if you're in the mood to shop for art supplies. Both Dick Blick and RSVP in Iowa City are doing curbside pick up.
Of course the rainbow display is inviting, but it's also inviting to children when you let them use the good/fancy art supplies. It's ok to give some guidelines about how to use them. I also recommend thicker paper for this invitation - such as watercolor paper.
For a related read aloud video see: Monsters Love Colors
Art Studio teacher