Mk1 Golf GTi - 1.8 DX - Green Deposits Ignition System

Hi all, need some help please.

I have been through 2 sets of leads in the past 2 years, NGK and most recent Bosch. Also 2 new dizzy caps.

I notice both new leads are left with green deposits, including the dizzy cap and today I noticed inside the coil.

Is this green deposit issue cause of a faulty coil? Should I replace it?

Appreciate your assistance.

Thanks

corrosion . clean it including the inside of coil, then use some di-electric grease to prevent....

afterwards spray with battery corrosion preventative paint

Thanks, I have been having this issue for a long time.

Any recommended brand for the dielectric grease and battery corrosion preventative paint.

Not sure on the grease, but way back I used to use Holts Damp Start to seal everything.