Hi Malone,
Yes, I did have my pens at the ready but, alas, they've not been used 😢
I have the instructions (iterates insinuate altitude and drench the lattice), but can't see how they apply to the grid and there's definitely no mention of a colour - although I can see one written in the NE going down.
Obviously I'm in a group of one so I know it's me being dense so I'll look at again today and hopefully I will have a Eureka moment:-)