Make a 2-D array of strings. I would color the background transparent. That way you can overlay it on top of a 2-D array of booleans or color boxes.
Generate 2 random numbers from 0 to 5. They would be your row and column indices.
Now set up a routine to change the color of that element in the 2-D array of color boxes (or true/false of that 2-D array of booleans) so that it appears like it is flashing for how long you need it to.
