Add color property to the categories in license-classifications.yml

[tsteenbe]

Edit: But maybe we could add a color property to the categories in license-classifications.yml, and make use of them here.

Originally posted by @sschuberth in #4092 (comment)

[sschuberth]

@tsteenbe, given that it's good practice to separate the data model from the visualization, I don't believe anymore that adding a color property to the license classification would be a good idea. If you agree, can we close this issue?

[sschuberth]

As discussed in the community meeting, it's no the ORT configuration model that should associate colors (or in fact any visual representation) to semantics of the license classification. Instead, this should be a reporter-specific feature. In case of the web-app reporter, the proposal is to solve this via #2643 instead.