Being German, I would be more surprised if anything work related wouldn't have a professional standard, e.g. the DIN norms. They exist for everything basic, like business letters (DIN 5008), up to high level concepts like project management (DIN 69901). So of course they also exist in various forms for office equipment. Typically they are created by small committees of experts who more or less formalize what they think is fine.
With Germany's heavy focus on industry, I could also imagine that having neutral colors generally in all settings was seen as a safety feature by itself because they make it easier to spot colors for warning signs (which you'll have around if you use the computers in a mixed industrial setting).
With Germany's heavy focus on industry, I could also imagine that having neutral colors generally in all settings was seen as a safety feature by itself because they make it easier to spot colors for warning signs (which you'll have around if you use the computers in a mixed industrial setting).