Creating A Traffic Light?

Simulate a traffic light with three text boxes placed vertically on a form. initially, the bottom text box is solid green and the other text boxes are dark grey. when the tab key is pressed, the middle text box turns yellow and bottem box turns dark grey. next time the tab key is pressed, the top box turns red and the bottem two turn dark grey. Basically the tab key cycles through the colors.First off let me say im not looking for an entire code. What im looking new to VB (been working on it for only a week) and im haven trouble finding a sourcecode for "tab". I named the bottem text box "Green", middle text box "yellow" and top "Red"....how do i go about finishing the code?

Public Class trafficlight
Private Sub Green_BackColorChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Green.BackColorChanged

[code].....