I normally wouldn't get involved in these conversations as they are usually a minefield of problems, but I think that there is a point here that many posters are missing.
I work for a large corporate company, and every quarter we have to do online 'compliance' training, part of which involves sections on discrimination in the workplace. We are told very clearly that we should always avoid referencing anyone by their skin colour, sexual orientation, or religion in the workplace. In fact, they have an example scenario very similar to this where a visitor asks you to identify a particular colleague, and the guidance is very clear that you should say things like 'the person on the left', 'the person in the blue shirt', etc. In fact they go on to say that if there is still confusion the best solution is always to go over personally and introduce them rather than falling back on skin colour or similar.
Everybody in the company does this basic training, and senior management have much more focused and detailed training in this area as their positions of authority and responsibility mean that they are held to higher standards and their actions can have very severe ramifications for both themselves personally and also the company (lawsuits, negative publicity, etc).
I mention this because last night those officials were representing UEFA in a professional environment and were in a position of severe authority. They should have known from their training that referencing skin colour when referring to players or coaches was simply not acceptable. Before resorting to mentioning race they could have pointed, said ' the guy third from the left', 'the guy with his face mask around his chin', 'the guy in the Puma boots', etc. If that still fails, then simply walk over and identify the person at close proximity. There is just no reason to mention race.
So there are two possibilities here. The first one is that UEFA does provide their matchday officials with training in this area and the 4th Official simply ignored it or forgot it, in which case he is responsible and should be held accountable. Alternatively, UEFA doesn't provide their officials with this kind of training and so they should be held responsible and are not taking these issues seriously enough, which would be pretty damning give the number of UEFA lead anti-racism campaigns there have been.
Whether or not the official is racist or meant to cause offence is irrelevant in this instance, and instead it is the fact that he has failed to live up to the standards that should be set by people of authority in a professional environment, and that those actions could cause offence as a result.