MATLAB GUI - Geometrical shapes and changing their color

Hello! I have to make a small project for university but the teacher didn't work with us in MATLAB GUI so i have absolutely no idea. I have to draw 6 geometrical shapes (like a square, circle, etc) using the FILL command and by using a button. For exemple: When I click on a pushbutton with the name "Square", it appears a square. For this I made something like this:

function square_Callback(hObject, eventdata, handles)
axis([0 10 0 10])
hold on
fill([2 8 8 2],[2 2 8 8], 'r')

But now it comes the hard part. I have to make a button and when I click the button, the square changes its color, let's say from red to yellow and also, another button that changes the background color. Can you help me please?