Prepare the poster board before preschool hours. There are seven colors in the rainbow: red, orange, yellow, green, blue, indigo and violet. However, for preschoolers, it is easier to understand the rainbow with six colors ending in blue and purple rather than differentiating among blue, indigo and violet. With the permanent marker, draw six joined arcs about 1 inch wide. Write the color's name in each arc to designate the order of colors in a rainbow.
Gather rainbow-colored items that will be easily glued to the poster board. Items that work well include yarn, magazine cutouts, dyed macaroni, tissue paper, fruit loops and beads. You may pre-sort these items into bins of each color or allow your preschoolers to enhance their learning activity by sorting the items themselves.
Place the prepared poster board on the floor or a table that provides all children access to the poster board at one time. Arrange the bins of sorted material in the designated activity area with one glue container for every two children, allowing enough glue for the class while encouraging sharing and taking turns.
Demonstrate the object of the activity. Show the children how to glue enough items into the arc to fill in the rainbow and that each colored item should go in the appropriately labeled arc.
Challenge your preschoolers to use their budding reading and language skills to figure out which arc is labeled for which color. Help when necessary to keep the children from becoming frustrated, and encourage more advanced readers to help their classmates.