Using Java language...

Make a windows program in Java that has 4 buttons labeled button 1, button 2. button 3 and button 4 on it. Have these controls in one panel on your frame.

Simulate making controls under a menu to allow real world users to change the screen so they can see it better based on the lighting conditions in the work place and possibly the vision requirements they have. In this case you would change multiple controls at one time.

Feel free to use any controls you wish on another panel to manage color and font changes.

Have controls to make the following changes by the user:

1) Change the Background color of all of the buttons at once to a color the user chooses.

(I would use a color chooser here. You could use a control or controls that gives the user some set choices.)

2) Change the font size of all of the buttons at once to a font size the user chooses.

(In the real world I would use a list box here but you can have them give the size by a textbox if you would like.)