I remember many years ago, when I prepared for a talk on coordination chemistry I found a PDF with a theory about how to predict the colors of simple coordination compounds. I remember the name of the person, who came up with this theory was a Nordic name, like Jorgenson. It sounded pretty similar to that at least but I cannot find it.
Basically, this was a quite empirical route. The metals had different numbers for each oxidation state and the ligands as well and in the end you had to either multiply or add them together (I don't really remember) but you came up with an energy which was sometimes close to the experimental value and sometimes completely wrong.
I know this is not really a good concept to use but I am more interested in the theory itself and would like to add it to a recent summary on coordination chemistry I am writing right now. Perhaps somebody has heard of this theory before.