Hunt for blue treasures all over the classroom to learn to identify the color blue. Turn your class of preschoolers loose in the classroom with the instruction to find blue colored items and bring them to a designated area. Create a pile consisting of the blue items the children found. Seat children in a circle around the pile of blue things. Pick up objects, one at a time. Let the child who found it tell what it is and then put the item back where it belongs.
Provide preschoolers with an assortment of blue foods to sample in class at snack time. Set blueberries, blue-corn tortilla chips and fat-free sour cream dip, tinted blue with a drop or two of blue food color, on a table. Blue fruit snacks, blue-tinted sugar cookies and blue gelatin are preschooler-pleasing blue foods to consider serving.
Place similar objects---blocks, balls or other small objects---in a shoebox. Challenge one or two preschoolers at a time to sort through the objects and take only the blue things out of the box. When a child completes the task, reward her with a blue star sticker.
Drain a can of blueberries, saving the blue colored water that you pour from the can. Smash 10 of the blueberries and mix them in the blue water. After covering a work surface with newspaper and covering preschoolers clothes with paint smocks, give them white paper and paintbrushes to paint pictures with the blueberry paint.