[NHCOLL-L:2036] stained paleo. specimens

[Invert Paleo2]

In the Fossil Invertebrates collection we have several limestone 
Blastoids and Crinoids that have be stained with what appears to be 
green food coloring at some point in the past.  I have attempted water 
but it does not remove the dye completely.  Some of these specimens are 
also  repaired with glue so I am wary to use  any solvents.  Do 
researchers find this distracting?  Should the staining be removed?  If 
so, what is the best method? What are some collections policies in 
relation to alteration of this nature?
Thank you,
Amy Singer