I would second for the brown filter. I, too, went through almost all the filters and settled with Brown.Yeah, what @povidlo said. It's not that long of a thread and all your questions are addressed. I'm pretty sure there's even talk about the 535 Reds. I have never felt the need to swap the cables on these phones. As far as filter, I used Green for a while, but when I swapped them out with Brown, I had what was so pleasing to me, I stayed with Brown. The filters were not expensive when I got my first ones from Mouser.com and even cheaper when I got more from AliExpress. As you can read in previous posts, removal of the filters is not difficult, you just need to be steady and patient. I used a sharp needle. Have fun and give us a review when you're done!
I was using some precision screw drivers (those ones for fixing my eye glasses) to remove the filters. I wasn't able to save the stock filters. One of them was damaged during the initial removal.