You may wish to make a scoring chart, showing staining levels for unripe, ripe, and several intermediate levels. At a minimum, score your fruit as unripe (0), somewhat ripe (1), and fully ripe (2). This way, you are assigning a quantitative value to the data so that you can average the value for ripeness of the control and test groups and can present the results in a bar graph.
Test Your Hypothesis
If the ripening of the fruit was unaffected by storing it with a banana, then both the control and test groups should be the same level of ripeness. Were they? Was the hypothesis accepted or rejected? What is the significance of this result?