In the 1800s postage stamps were issued to be useful, not to be collected. When a country reprinted a stamp, often a new color that was slightly different from the original was used. This leads to some valuable rarities.
In record covers, the same thing happens. All kinds of variants exist – check any catalog of Elvis Presley records. For Elvis collectors, major and minor variants are things they want.
All sorts of variants exist on Classical covers too, but nobody collects them. Which is fine in my opinion. Here I show three Columbia Masterworks llps, ca. 1949. For one of them I have the generic cover – tan this time instead of the blue ones I showed earlier. Then each of these three lps has slight color variants.