A colorful project report is not always the most informative, depending on the information you are trying to communicate. Take this Gantt chart below as an example:

It’s clean and attractive, sure, but if you look at the legend in the lower-left hand corner, you will see that we are color-coding by the number of hours spent on each task. The color scheme doesn’t intuitively tell us which tasks take more work than others. Viewers have to look back and forth at the legend to get this information, which creates unnecessary whiplash on the eyeballs.
Consider this alternative:

This is the exact same Gantt chart, but we’ve replaced the unhelpful rainbow theme with a grayscale representation of hours required per task. Tasks requiring the most work are the darkest, which helps us immediately identify that “Task 9” is going to take significantly more time than everything else in the project.
“Task 9” also happens to be one of the shorter-duration items in the project plan, so the grayscale approach to hours of work really helps it stand out where it wouldn’t have in the more colorful approach.
If you think gray is boring, we won’t argue with you. But luckily, you can show the relative size of different aspects of your project without feeling like you’re publishing an old newspaper. Here is an example of the same project color-coded by cost instead of hours:

Here, we’ve used a “greenscale” approach instead of a grayscale approach. It’s a little more lively, and since people think of green when they think of money, it’s a good choice. Again, we immediately see that a relatively miniscule task (“Task 6”) is eating up significantly more budget than everything else in the project.
So, color isn’t always bad, but it needs to be used the right way, in service of what you are actually trying to present. When building a project report, ask yourself which of these types of dimensions best applies to the way you want to assign color:
- Categorical: These dimensions of your project create distinct categories, but doesn’t have any real order or scale. Status, resources, subprojects, and clients are good examples. Choose distinct, vibrant colors for these so that they will stand out from each other easily.
- Interval: These dimensions of your project have clear numeric values attached, such as cost, hours, percent complete or slack. Choose grayscale or a single color with different levels of saturation to represent the high and low ends of the scale of values you are reporting.
- Ordinal: These are less common in project management, and are typically limited to sequences (1, 2, 3). Examples include a sequence of phases or milestones. We recommend a distinct, vibrant palette (like categorical) for these so they are easy to spot, but without inadvertently implying scale.
In short, if there is some sense of scale to your project variables, you should use a grayscale or color scale to represent them. If not, you can stick to good old-fashioned color coding.