Pin several different colored fish-shaped cut-outs onto a bulletin board covered in dark blue paper. Decorate the fish with wiggly eyes and teach the children a simple rhyme. Choose a story such as "Brown Bear, Brown Bear What Do You See?" by Bill Martin, Jr. and modify it, replacing "brown bear" with "red fish" or the appropriate color. So you could say, "Red fish, red fish, what do you see?--I see a blue fish looking at me."
Creating a caterpillar on a bulletin board with different colors for each part of its body is a good way to teach preschool children their colors. Cut out enough circles in each color to create the caterpillar's body. Arrange the colored circles in a pattern with a big caterpillar head at the beginning. Start from the head and go through the colors with the students each day, teaching them color recognition.
Create a bulletin board with differently colored spring flowers. Cut the flowers out of construction paper and cut green stems for each flower. Arrange the flowers on the bulletin board with a saying such as "Spring Has Sprung" across the top of the board. Discuss the different colors with the class and encourage the students to name each color.
Create a large brown Easter basket out of construction paper on a bulletin board. Cut Easter egg shapes from various colors of construction paper. Hand each preschool student a cut-out of an Easter egg and allow them to decorate the egg with markers or crayons. When the class has finished decorating their paper eggs, call out a color and instruct the preschool students to come up to the board if they have an egg of that color. Hold up each egg and ask the class if the color is the correct one. Assemble the eggs in the basket according to color.