That approach is no good for multiple treatments, because there'll be too many groups and not enough subjects in each group. One solution is simply to plot the means for each treatment. Connect all the points together, as I have done in the figure, to show they all have the same repeated-measures relationship to each other. Or if the treatments can be put into a sensible order, such as an increasing dose of something, plot the treatments in order along the X axis and connect the points sequentially. Either way, you shouldn't use a bar graph.
Standard deviations are a problem with multiple crossovers.
You could plot the standard deviations for each treatment, but they will be inflated by any learning effects. This SD includes within-subject retest error, but it is not affected by the treatment and learning effects. It's therefore the best measure of variation by which to assess visually the magnitude of the treatment effects shown in your plot. In the text of the Results section, give the raw differences between the means for the treatments and the confidence intervals for these differences. You could randomize one subject to each sequence of treatments, but you might not need 24 subjects to get acceptable confidence limits for your comparisons.