Hardieplank is grey, porous, brittle.
Installation consists of preparing the surface and properly attaching
the planks. Now it's on your house. All seams and nail holes must be
caulked and the surface painted. Will you use one subcontractor for all
the work? That would be preferable. You don't want blame-shifting when
something does not turn out right or warranty work is required.
This material will require eventual maintenance - patching any cracked
surface, recaulk and repaint. You should understand what reasonable
expectations are for this to be normal and not a failure of the
installer to correctly install and finish the product.
Will you subcontract any repairs due to unavoidable damage?