Black or red rubber flashings- the roofers choice!
Roofers love to use rubber flashings for your chimney because they are slightly easier too install with little skill (that's the only reason I could come up with).
Here are the reasons you should say NO:
They are not compliant for 4 reasons-
they do not allow free passage of air to cool the chimney- chimney can overheat presenting a fire hazard.
the black one is combustible -it can melt.
chimneys can only be installed with the parts supplied by the same manufacturer that made the chimney!
they are not structurally strong- they collapse under weight of snow.
It is not really a difference of opinion. Just don't listen to the roofer. Read the instructions that you get with the chimney. Or later when inspected you will find out the hard way.