You could get some white greenhouse paint which can be bought from such as wilkos cheaply

That's probably the easiest way to do it and it washes off in Sept/Oct, easy as anything. Failing that, green shade net stretched across the OUTSIDE of the glass and secured somehow.

You can buy clips for the shade netting at the same place that you buy the netting.
I want to use netting over the lower section of roof of the greenhouse and partway down the side (2m wide will do this). I ask, is there anything to cap the lower end of the the metal roof frame so that it doesn't cut the net?

I used a piece of rubber pond liner folded over the end. Heath Robinson's got nothing on me!

Thanks.