UML color standards are a set of four colors associated with Unified Modeling Language (UML) diagrams. The coloring system indicates which of several archetypes apply to the UML object. UML typically identifies a stereotype with a bracketed comment for each object identifying whether it is a class, interface, etc.
These colors were first suggested by Peter Coad, Eric Lefebvre, and Jeff De Luca in a series of articles in The Coad Letter,[1][2] and later published in their book Java Modeling In Color With UML.[3]
Over hundreds of domain models, it became clear that four major "types" of classes appeared again and again, though they had different names in different domains. After much discussion, these were termed archetypes, which is meant to convey that the classes of a given archetype follow more or less the same form. That is, attributes, methods, associations, and interfaces are fairly similar among classes of a given archetype.
When attempting to classify a given domain class, one typically asks about the color standards in this order:
Although the actual colors vary, most systems tend to use lighter color palettes so that black text can also be easily read on a colored background. Coad, et al., used the 4-color pastel Post-it notes,[4] and later had UML modeling tools support the color scheme by associating a color to one or more class stereotypes.
Many people feel colored objects appeal to the pattern recognition section of the brain. Others advocate that you can begin a modeling process with a stack of four-color note cards or colored sticky notes.
The value of color modeling was especially obvious when standing back from a model drawn or projected on a wall. That extra dimension allowed modelers to see important aspects of the models (the pink classes, for instance), and to spot areas that may need reviewing (unusual combinations of color classes linked together).
The technique also made it easy to help determine aspects of the domain model – especially for newcomers to modeling. For example, by simply looking first for "pinks" in the domain, it was easy to begin to get some important classes identified for a given domain. It was also easy to review the standard types of attributes, methods, and so on, for applicability to the current domain effort.