Hi there! Late to this thread but want to share some things about the Gold colors and the Modern Buckle because I can't find good info or photos elsewhere on the web and I'm sure other people are also looking.
Apple only made two Modern Buckles with a "Gold" stainless color on their hardware: the Aubergine and Raspberry bands, released over the lifespan of the Apple Watch Series 5 (Fall 2019, Spring 2020). The hardware on these bands is a perfect match for the finish of the Series 4 and Series 5 Stainless Steel Gold Apple Watches, which had more of a champagne gold hue.
Starting with Series 6, Apple changed the shade of the Stainless Steel Gold color to be more of a neutral yellow gold. This shade does NOT match the hardware on the Modern Buckle very well. My wife has tried her gold hardware bands on the Series 6-9 in the Apple Store over the years, and there is an obvious, notable color clash similar to what you would find between the Series 10 Natural Titanium and previous Stainless Steel Silver models. You can see this clash in the above photos posted by Beachmusic18—the champagne gold of the Modern Buckle hardware does not match the yellow gold of Series 6-9, and is notably darker. This visibility of this clash depends on lighting conditions, but in bright environments will be obvious—to you, though. Unless somebody is being creepy they're not going to be close enough to notice!
With the Series 10 and shift to Titanium, Apple has chosen a shade somewhat in between the champagne gold of the Series 4-5 Stainless Steel model and the yellow gold of Series 6-9. In the attached photos, you can see a Series 10 Titanium Gold watch with a Modern Buckle equipped with gold hardware. The finish, while not a perfect match, is much better than the match offered on the Series 6-9, and is not obvious in the majority of lighting conditions.
If you are looking to match your Modern Buckle hardware to a new, Gold Apple Watch, you should get a Series 10.
Now, you might notice that the band in the photos is neither Raspberry or Aubergine. That's because, with care, you can remove the hardware on these bands with the right screwdriver. There's another thread on here in which the process is documented. For the most part, it isn't too difficult and can be done in a few minutes as long as you're careful—the biggest obstacle will be stripping the screws, which are secured with an adhesive, but this is only an issue on the earliest generation of Modern Buckle bands which have far more adhesive than those released later.
How do I know this? I've done hardware swaps on several colors of Modern Buckle for my wife, who has a Series 5 Stainless Steel in Gold.
Her collection is in the attached images. I'm still trying to track down either a Cape Cod Blue/Azure band and a Marigold band to do the swap on, and have extra Raspberry bands if anyone wants Raspberry band with silver hardware. I know we're not really supposed to be soliciting here (sorry mods), but I've also put the Gold Modern Buckle hardware on bands for others before, and am happy to work out an arrangement over PM if there's a unique color you'd like to have in Gold.
Anyway, I hope this is helpful for those moving from a Series 4-5. I recommend getting the Series 10 over a Series 6-9 because it's definitely a better match. So long as Apple sticks with the current gold color and band attachment system, you should be able to get at least another 5 years out of your matched Modern Buckles.
