I would go the red medium with gold hardware given that you already have a bag with beige/gold and black/gold. I think red would be more versatile than pink as well. Would you be buying from a reseller? I haven't seen red with gold hardware in quite some time.
Definitely get the red! A bright red with GH is my ultimate HG. But all the reds now are with SH. If you're fine with that, then go for it. I just saw the 12A red & it's gorgeous! All the customers at the Chanel boutique were gathering around me as I tried it on & everyone was an enabler!
The red would be a wonderful addition to your collection. You already have a black & beige, so I ruled those out. I have both the pink & red, but I don't think you should get the pink before the red because it's just not as versatile or classic. I think your collection would be complete & well rounded with the black, beige, & red.