They used the colors which had the best contrast against each other and if there was a driver issue, colors which looked the more appropriate in greyscale. Driver issues, forgotten today, drove most architectural decisions at Microsoft. The core word they used was ‘working with partners’. People used to bring it up all the time in interviews in the 80s regarding PC’s but not all in one computers like Apple and to a degree amiga. I remember people used to watch football on television on portable tv’s which was only made possible because the jerseys had a light and dark version which visiting teams would get to choose which one they get.

There is a reason why they're the most ugly colours. Windows 2 only can display 8 colours: CMY+RGB+Black+White. Cheap colour monitors had only four input pins - RGBI - and could at best display those eight colours, plus a darker version of them.