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).
The only modern reference I could find is about keyboard colors in the "DGUV rules for the office business sector" [0], quote from page 38:
Benefits of light-coloured keyboards
Light keyboards with dark lettering are better suited to
the use of true video on the VDU, i.e. dark characters on
a light background. They avoid disturbing differences in
brightness and thus save your employee's eyes unnecessary adaptation to these differences. The surfaces of
keys become shiny after longer use, as a result of either
wear or sweat from the fingers. This is less apparent on
light keys than on dark keys.
PS: the start is a bit poorly translated, the German original [1] is:
Vorteile von hellen Tastaturen
Helle Tastaturen mit dunkler Beschriftung passen besser zur Positivdarstellung am Bildschirm (d. h. dunkle
Zeichen auf hellem Untergrund). Sie vermeiden störende Helligkeitsunterschiede und ersparen dadurch den
Augen Ihrer Beschäftigten unnötige Helligkeitsanpassungen (Adaptationen). Tastenoberflächen glänzen bei
längerer Benutzung entweder infolge von Abnutzung
oder durch Fingerschweiß. Dies fällt bei hellen Tasten
weniger auf als bei dunklen Tasten.
...the first part that's poorly translated is basically that if you use dark letters on bright background on the display, it's better if the keyboard is also dark letters on bright background so the eyes don't need to adjust too much.
...which in turn means that coders are probably better off with a dark keyboard ;)
I don't think any coder (or any professionnal required to type a lot) need to look at his keyboard anyway, I don't think their eyes would suffer regardless of the color.
What the actual
How? Why?
That’s so bizarre.