Choosing paint colors can be an enterprise fraught with significant (other) danger and considerable expense. (Need proof? Consider the pyramid of too-bold, not-bold-enough, not-quite-right, paint cans ...

You spent hours choosing the perfect paint color and covered every wall with care. But years later, a touch-up is needed—and you can’t remember if the shade of green was Phantom Mist or Dinner Mint.

It’s an inevitability of home ownership that your walls and furniture will see normal wear and tear that require paint touch-ups at some point. But if you don’t have the original can of paint or color ...