Greetings again, SE!
This may or may not be a bug, but I'm leaning towards "is a bug".
The crafting training "Dyeing" doesn't seem to be listed in a recipes actual requirements in-game. However, anecdotal observations by players are showing that having the Dyeing training book makes things like colored leather and cloth significantly easier to synth.
Fansite Databases such as ZAM and YG do list Dyeing as a requirement for dyed materials, but that's only due to the observations of the players and not because it's listed as such in-game. As far as I can tell, no recipe in-game calls for Dyeing (correct me if I'm wrong here, fellow forum-goers)!
Is this a bug? Are things such as Woad-blue canvas and Moss-green buffalo leather supposed to list Dyeing as a requirement?