I have an assortment of Honda bikes, so I wanted the spec manuals to cover them. I bought the 3 grey ones in this photo for the different date ranges, but the little one was the only copy I have seen that is grey, all the rest I see listed are the red one. Being curious, I bought one of the red ones to compare.

The contents are the same. There are different markings on the cover, as apparent in the picture, but the back cover of the grey one has an item number also.
Anyone know why the difference in cover?