The color on the face of the sight is just a personal preference,,gold or silver,,white,,red,,ect.
14k gold will tarnish quite easily especially when exposed to BP fouling.
(14k is 14/24 pure)
It's about the color of a lot of brass alloys anyway. Brass wire has been used many times and passed off as 14k gold wire in engraving work because of it's look.
Either the 14k or a brass faced small edge can be brightened up with a quick rub w/a piece of leather.
24k is pure gold (24/24) and won't tarnish. A tiny, thin flake soldered to the face of the sight isn't a WellsFargo supply run.
But finding some in that small quantity is difficult
Silver,,, coin, sterling and even fine silver are subject to tarnish but again the simple rub will bring back a glow to them.
The new 'stay-brite' lead free soft solders are just that,,they don't tarnish and are nice for the pin point dot on front sites.
I use it to replace the silver dot on a lot of front sites from 22's missing them after they've gone thru hot bluing. Easy to work with,low melt point, ect.
Scrape the face of the site clean, flux it,,tin the soldering iron and just touch the tinned tip to the site for an instant to transfer a dot and you're done. A nice round standing bead of 'silver' for a site.
Don't forget ivory as a sight bead either,,though the new Fed regs are imposing and scary when you get into them.