This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Don't like it. doesn't look like object-oriented programming to me. You ought to have an array of buttons, and you should be adding a listener to each. Your listener can alter the text colour as well as the letter.