There are two issues here:
1) Is the color (blue/cyan) of the ink visible to the copier light? If it is then the copier will reproduce it. Modern photocopiers "see" cyan/blue so they will reproduce it. The notion of non-repro blue is not applicable to modern copiers/scanners.
2) Is the resolution of the copier's sensors high enough to reproduce a fine screen? There are no guarantees. If, for example you make your graph paper using a 175 lpi 10% screen (any color) then some copiers will be able to reproduce it, some will reproduce it as a patchy graph, and some will not "see" it and therefore can't reproduce it.
In short there are no guarantees of non-reproducability.
If you do not use a PMS ink to make your graph lines but choose to halftone screen them then you will have to be careful about the lpi to line width relationship otherwise you will get artifacts in the lines (ribboning, line width variations, etc.)
IMHO you need to run a press test to figure out the specifications. Even so you will not be able to guarantee performance (the graph won't reproduce) to your customer.
best, gordo