I think it's the purple wire to ground turns in on.
Performa 6200's aren't the most amazing machines to see in action. They're often considered one of the worst Macs ever made.
It might be wise to invest in a DB-15 to VGA adapter. The Apple made ones "just work" but are hard to find(the only one I have was packed in the accessory box with my B&W G3). The cheap ones with DIP switches will work, but often require some fiddling to get the adapter to work correctly.
I have a genuine DB-15 to VGA adapter... It's the transparent yellowish-beigeish whateverish color one. Are these rare?
Not to my knowledge. I have 2 of them. Both of mine have switches to control the Resolution on the screen. Before i even got a beige Mac i recieved 2 of them gave one away and when i bought my Beige G3 it came with one too. NOt that rare..