Here's a little bit of color theory at you.
No way will you get a red lens to flash the amber you are looking for. Part of it is color, the other part is "value"; a certain amount of density or transmission of light is held back by the darker red lenses as compared to the lighter amber lenses. At best you might get some kind of muddy dark yellow/amber which would not be what you are trying to achieve; might even be worse.
That being said, as a driver I don't see the rear lenses; the person behind me does. So, Steve, with the same idea as you vis safety, some years ago I sold my original all red lenses, got a
LOT of money for them, took about 1/3 of the proceeds and bought nearly new amber ones on eBay. A year later, seeing an opportunity, I sold those on eBay, and managed to find a fellow Pagoda owner unloading a NOS amber set new in box, and I made a few dollars on that deal too. End result after the wheeling and dealing was some excess funds and all new amber tail lamps--with my original goal of safety achieved--in theory at least. Never been hit though!
All of the "profit" went into the endless list of stuff I am always needing to buy for the car...
I did not go to Rio with the profits.