I was just thinking about this myself. I also occasionally buy backups of the exact item/color if I can find one secondhand or on final sale AND it’s likely going to be difficult or impossible to replace.
(And of course, basics like intimates, tees, pajamas, socks…)
Some staples that I have multiples of in different colors because I use them a lot, and found other colors secondhand:
• ECCO Soft 7 sneakers
• Rebecca Minkoff Leo envelope clutch
• Frye Elyssa oxford (a discontinued style)
• Cole Haan Air Tali wedge pumps (also discontinued)
• Lucky Basel bootie
• Connally McDougall Sadie midi skirt
• A Caslon suede flat mule from a Nordstrom Anniversary Sale many years ago
• So many activewear pieces - leggings, bodysuits, jackets, shoes
• I can think of several tops, shirts, dresses, or skirts where they worked so well on me that I’ve bought dupes in different colors.
Duplicates of the exact item due to being discontinued and wearing out when I found it secondhand or on final clearance:
• Ecco Flash T-strap sandal in silver - not the one that’s being made now, but a much older style. I’ve found a couple pairs secondhand and new or worn once or twice for an incredibly cheap price.
• Seychelles So Blue Metallic bootie (I wear these all the time, and my pair from 2017 or so is getting very very worn out!)
• Jeans, when I find a pair that works on me & that I wear all the time.