painted on top of that

22:52 Apr 7, 2020 

Thank you all.

15:52 Apr 7, 2020 

Thanks a lot!

15:36 Apr 7, 2020 

explanation.

15:28 Apr 7, 2020 

Not really... because it changes the slant of the text.

There is a grey painted area representing his brain, and on top of this there are other coloured areas representing the activities — we see: the emphasis is on the painted elements, the 'we see' is fairly incidental; it might equally well be written 'there are', as I have shown.
By bringing the 'we see' to the head of the clause, you give it greater prominence — from being almost a "throw-way" aside, it suddenly appears to have a lot more importance than intended; it's as if you said "we see red patches, but what we don't see is the green ones"