Chapter 2.3, Problem 40E

In Exercises 39 through 44, write a program to carry out the task.

Simulate a traffic light with three small square text boxes placed vertically on a form. See

Fig. 2.29. Initially, the bottom text box is solid green and the other text boxes are dark gray.

When the Tab key is pressed, the middle text box turns yellow and the bottom text box turns

dark gray. The next time Tab is pressed, the top text box turns red and the middle text box

turns dark gray. Subsequent pressing of the Tab key cycles through the three colors. Hint: First place the bottom text box on the form, then the middle text box, and finally the top text box.