I worked at Umbro at the time and this was a bog standard kit used by amateur clubs, in boxes of 12 IIRC and selling at little more than £10.00 apiece wholesale .
The line was called Napoli and also came in sky blue with navy collar and cuffs and red with white collar and cuffs. This one was technically amber and navy (and was similar to Oxford United's shirt:
https://oxfordkits.com/1985.html) which is why the yellow shorts and socks don't match - so not all-yellow!
The shirts were taken off the shelf and simply badged up.
But the point of this kit wasn't to wear it at Highbury, where there would have been no colour clash, but Hillsborough on New Year's Day where there would have been, given that the away shirt was maroon and white stripes.
Peter Swales was purported to have said we would never wear yellow again.
In the event, a new, more professional maroon kit was devised and worn at Hillsborough.
I was at Highbury on that infamous afternoon. However, I got there late due to a catalogue of travel mishaps and missed the kick-off but thought I'd somehow gone to the wrong ground!