Acorn's line of ARM-based Archimedes computers was common in UK schools in the 1990s, and many classrooms had an A3000, A4000, or A5000 computer.
The function keys of the A3000 were a distinctive red colour:
(image from Wikimedia Commons)
The A4000, and A5000 (pictured), had dark grey function keys, similar to PC keyboards:
(image from Wikimedia Commons)
Why was the A3000's keyboard so colourful by comparison?
The red function keys were a carry-over from the days of the BBC's Computer Literacy Project.
The first computers made for the BBC by Acorn, the Model A and Model B featured red function keys:
These red keys were a feature of all "BBC" computers, including the subsequent BBC Master series.
The first machines of Acorn's Archimedes line were the A300 and A400 series. The A300s had red function keys, as they still carried BBC branding. The A400s weren't BBC branded, and thus didn't have the red keys.
If you look closely at the top-right corner of the A3000's keyboard (see image in the question), you'll see the logo of the "BBC Microcomputer System" next to the A3000 logo. The A4000 and A5000 weren't marketed as BBC machines, and thus, like the A400 series, they weren't allowed to have red function keys.
The BBC micro series had red function keys. Exactly why the function keys were red seems to be lost to history; there doesn't seem to be any mention of such in any of the BBC specification documents that have been released. Nevertheless it became an iconic feature of the BBC micro.
According to an interview, the Archimedes was originally conceived as an office automation machine, running an OS called ARX that never saw the light of day.
Acorn later decided to make a "BBC like" OS for the machine and pitch it to the BBC as the successor to the BBC micro. The BBC showed interest and the 300 series Archimedes machines were released with BBC branding and red function keys. Meanwhile the 400 series, which were aimed at more professional markets had grey function keys.
The A3000 was the successor to the 300 series and continued with the BBC branding and red function keys. It was the last Acorn machine to used the BBC brand.
The next generation, while dropping the BBC brand, actually expanded the function key colour code. The A3020, which was aimed at schools, kept the red function keys. The A3010, a lower end model aimed at home users, went with green function keys, and the A4000 kept the grey function keys of previous "business" models.
Sadly that seems to have been the end of colourful function keys at Acorn.
