Ah, now I understand what you mean. It is certainly true, that there is additional information in a diagram. But - most of that information is just visual help

Ah, now I understand what you mean. It is certainly true, that there is additional information in a diagram. But - most of that information is just visual help to transport the raw information - to enable you to decode the information (which is what this is all about, as decoding code is mental work). The x y position of a uml class diagram for example, is irrelevant in terms of raw data, but it makes a difference to the brain, of whether one diagram is centered or in some corner. Likewise all the other information, like color etc. They are simply there to help you understand the main information. So I do not think they carry unessential information. If the color of a diagram helps get the information across - meaning it makes it easier for the reader to understand the main information - than that information might be not essential, but still important. Whether that works, depends of course on the diagrams and tools and how they get used. Again, this is the hard part.