It wouldn't personally for me have been worth coaching the child to refuse because I can't think of a single situation prior to middle school when it ever came up and then only in the form of something like the botany coloring book.
That's amazing to me, that someone would offer a botany coloring book (unless it was in a private school setting, in which case I can understand and am envious). Today coloring books are offered everywhere-- at the doctor's office, restaurants, even recently at the bank. They appear to be the "shut the kid up" toy of choice at all sorts of establishments.
It's not that raising my kid is free of other challenges-- far from it. It's that I just don't want to dull his mind with coloring books, in addition to all the other challenges. Children are naturally very creative, in a way that is quite often dulled by adulthood, sort of the way many people learn to do math badly. Cookie-cutter "art" projects, coloring books, etc. can all combine to stunt a child's artistic development.
At a preschool my son was at around the age of 3, they used to do a lot of "art" projects, really carbon-copy crafts projects. They were along the lines of gluing eyes to egg cartons in the same places, painting things in exactly the same way, etc. They were pretty obviously designed to show the parents some output, not to encourage creativity or anything useful like motor development.
At the preschool my son was at last year, the same thing happened. Meanwhile there was a slavish adherence to multiple intelligences theory (which was not pushed so obviously in the initial information session or I probably would have taken my son elsewhere), and a complete lack of understanding of how to teach gifted children, how to foster a love of art, or anything else I would prefer my child to learn.
When someone offers a generic coloring book to my kid, I take it as a warning that they are simply trying to make my kid shut up and go away for a while, and/or that they don't know how to teach art, or what it means to be creative. Coloring, though it may develop some motor skills which can be developed in other ways too, is pretty much a non-thinking activity.
