Stacking the bars
The bars for each group in a bar chart can be stacked to help make comparisons between the groups. Stacked bar charts are particularly effective when the categorical variable is ordinal (has categories that can be meaningfully ordered).
The diagram below is a stacked bar chart showing the results from a questionnaire in New Zealand about women's ratings of their own body size. The 246 women all had similar body-mass index and were a little lighter than average for their height.
It is clear from this bar chart that there were more Europeans in the study than in the other ethnic groups. By stacking the proportions within groups, this information is lost but it is easier to see that a bigger proportion of Europeans believe they are overweight than the other groups.