Often times, those of us who are responsible for upward project reporting are unfortunately limited to the usable space we are provided to communicate.  Status, risk, issues, resources, and phasing are just some of the necessary dimensions of project data that may be required (even within a single slide) in order to provide our leadership with the information they need to help make decisions, remove obstacles, or ensure alignment across a portfolio.  Inevitably, we run out of white space for text labels or clarifying bullets, and in that situation the report will require a difference in formatting to provide meaning in the most efficient way possible.  Coloring, borders, shape, and label font are all examples of differences within our chart that may have separate meaning. Instinctually when a variation in formatting exists, our eyes will search for a legend to help us understand the meaning of those distinctions and for that reason a legend must always be present if we use formatting to illustrate meaning in our reporting.  Without a legend we may be inefficient in communicating our information, or will leave room for audience to make assumptions or have questions about the information.  Instead the communication should stand on its own.

Take this simple chart below with only 5 color differences, as an example.

In the first version we have no legend but have turned on a label column to the left with values that are driving the color.  I have to read and decipher the report in order to make an assumption that the colors relate to the Resource Name values in the column.  Even then, I will likely have an audience member ask to ensure the colors mean what they think they mean.  The Resource Names are also taking up valuable space on the left of my chart.

If I add the legend and remove the column I receive the information I need as a consumer to comprehend the meaning behind the formatting differences in a much smaller space, and at the same time room for interpretation or questioning has been eliminated…the slide now stands on its own.

Below is another example with only two colors, with their meaning populated in the column to the left, and without a legend.  Clearly, without the data column and without a legend we will not know what the colors mean, however, the data column is very bulky and contains only two values.  With the legend-version the column is eliminated and the clarification is very efficiently made.

While simplicity in our visuals is always the best policy, unfortunately our data is more often complex and therefore limiting our dataset within our reports to the extent that a legend won’t be necessary is virtually impossible.  Instead we must let the data drive the formatting (when we need it) to tell the story, and arm our audience with the tools they need to absorb it as quickly and easily as possible.  The legend is the most important of those critical tools.