Though that's a good site, they might well be wrong on that one, Les Motherby (who's most definitely our kit guru), states that in the 1921/22 season, the significant change for the season, was the switch to wearing white shorts with our amber and black striped shirts (rather than the black ones worn previously).
I wonder, as I wrote, who supplied the original information? And why it hasn’t been pointed out to them and corrected? May be wrong but I think that at one time it showed the blue kits in the 1930s as sky blue and later altered it to the aquamarine we wore. Which is funny, as the colours on the original Hull City locomotive, which was built the season we played in that different kit, were skyblue and white not aquamarine.