Color keys for large data sets?

Question

I have a task to create a day-by-day calendar list within a SaaS platform.

The calendar will encompass many different types of events and roles within the software. As part of this calendar, the Client feels it is important to show a color key for each type of event to clear up user confusion when quickly browsing events. For reference, a common use case would be that a user has 450+ events happening on a single day. There will be a total of 6 event types amongst the hundreds a user will see daily.

I've done a lot of digging for UI inspiration, and noticed something- most software does not include a color key in big or small event lists. I cannot find any particular reason that most mainstream software does NOT use a color key in their calendars. Perhaps this is because the data is not quite as large with what I am working with. Is there any reason people more seasoned than myself think that I should or shouldn't include a color key when defining event types?

Answer 1

Using colors a a single way to differentiate elements does eventually exclude color blind users. So it might be a good idea to us a second recognition to the elements. Something like a icon (if event types can be clearly associated with a symbol) or maybe even a label. Since we do not have a design you already made it is difficult to give a suggestion.

So to your question: I would say it depends on your users. You probably should test your design with real users. You will find out very fast if the miss a color key or other means of finding out what the meaning of the color is.

You might find out, that users do not care about the event types but only on the event time. Or the opposite that the event type is crucial. If so depending on the color only (as stated above) might be too less.

So alternatives to a color key could be a tool tip on the event. This might work well for users who use your system often since they will learn to connect the colors with the event types and will not be dependent to the tool tip after a while. If not so a color key would probably be the better choice since users will always depend on that information.

Answer 2

Color coding should only be used as a supplement to information that is available in other ways, for a few reasons:

• while most users can get value from color cues, not everyone can see them
• if you have more than about half a dozen colors, it quickly becomes hard to tell them apart
• it’s hard to memorize more than a handful of colors, and if you have to use a key then it defeats the purpose (which is to make it quicker to scan through a large number of items)

Calendar software commonly lets you assign colors to distinguish e.g. “work” and “personal” items; typically there is a detail view which spells out the label “work” or “personal” for each item, so you can easily find out what the colors mean. But since you have to memorize the colors anyway for them to be useful, there isn’t much point using up screen real estate for a legend.

Even if you’re not sure what the colors mean, they can still be helpful since the same event should have a consistent color. For example, if you are looking for future instances of “weekly sales meeting”, they should have the same color as the first instance. (If that is not the case, the color coding scheme may be counterproductive). For this purpose, again, you don’t need a key.

In short: the purpose of colors, icons, borders etc. is to save time and space, and if you really need a key, then that hasn’t worked (a key slows you down and takes up space), so you should consider just spelling out the information instead. You could do what GMail does with tags, and show the label on each item, but display the labels in color. This allows for quick scanning as well as making the meaning clear.

Answer 3

It's mostly about labelling colours. If orange represents sporting events, what colour does for me is to see at a glance how frequently sporting events are occurring in my calendar.

But if your calendar already has events labelled/ showing what they are, then the key is kind of just repeating, "look, orange represents sporting events... just in case you didn't know.".

A comparison of the two images below illustrates my point. The image on the left needs the key, whereas the image on the right doesn't really need it.