Colours and fonts
ISO19103 - Conceptual schema language - has one recomendation on font size in diagrams:
Recommendation 15: For the diagrams, readability concerns should be taken into account. Font size should be no smaller than 8 points after diagram scale is taken into account (a 12 pt font at 90% is 12*0.9 = 10.8 pt).
This recomendation also relates to the best practice Less is more. The diagrams should be of a size that allows them to be printed with the recomended font size.
The INSPIRE Repository tutorial have a convention to use
Arial as default model font.
It is recomended to follow this rule for all models.
Using different colours may be a way to communicate that some classes have been imported from other feature catalogues etc, but it is important to be aware that
colours are not a part of the model, they are only a graphical presentation. No model semantics can be stored in the colours.
Also, figures in ISO standards (the documents) shall not have colours. But colours can still be used in the diagrams, both for ISO models and other models. But the diagrams must be exported in black and white for use in ISO Standards and other documents with the same requirements. For example, for national specifications related to INSPIRE, one may use colours for INSPIRE classes. But always:
When using colours in diagrams: Provide a key (legend) for the colours.
ISO19160-1 - Addressing - Conceptual model - have reqirements and recomendations for documenting profiles of the standard. These may also be applied to other models (chapter 7.5.2):
To distinguish between base classes and profile-specific classes, it is recommended that a transparent background be used for (base) classes from the address model, and a shaded fill colour background for the profile-specific classes.
It is currently not possible to give attributes of a class different colors, see http://www.sparxsystems.com/cgi-bin/yabb/YaBB.cgi?num=1408114382/0#top and http://www.sparxsystems.com/cgi-bin/yabb/YaBB.cgi?num=1408101010/0#top