Blue Ink vs Black Ink

[ChipsteRJ]

I have some instructions:
DC, Waterfall & diapering instructions that are printed in both blue ink and black ink. Any way to tell whether these were photo copies vs being Genuine? I think the black ink ones are a brighter (not as much yellowing to the paper).

Were some sets of instruction printed in Black and others printed in Blue?

I am trying to decide whether I need to keep EVERY slight variant or not...

[Chrissytree]

I do have some in blue and others in black but I've only ever had one for each playset/ pony so I'm not sure if the same playset would have both colours.

[hathorcat]

I cant off the top of my head remember the complete list of which is which and I dont have all my scans on this computer unfortunately but there is a mix - some only were in blue, some only were in black and some came in blue and black. The main pattern seems to be that its blue for much of the early part of the line and black for later on but thats a general perception and there are exceptions to the rule.