Button properties

I have created a list of buttons where each button represents a module in the course. According to where the user is and has been in the course, the buttons changes color (from gray to navy). So navy is where the user is and has been and grey is what is coming next.The problem I am experiencing is that every time, in a new chapter I change the color from grey to navy, the same button changes color in the other chapters.What am I doing wrong? Any help, please?