Either put them aside for show only (and they're your tools, so whatever you like is a fine choice), or possibly re-ink the imprint when they inevitably get worn in use.
I dunno how Snap-on did it originally -- quite possibly hot foil transfer -- but for re-inking engraving or imprints on lots of things I use Lacquer-Sticks. They're available in a range of colors from a number of online sources, including the Big A.
These paint-in-a-crayon things work really well for stuff like this. Here's an example of the new thermo-mixing valve in my basement highlighted so I can see the directions for adjusting. As made, the valve had only the imprints, which were hard to see overhead in low light. The Lacquer-stick (white in this case) made the paint-filled lettering a lot easier to read.
(Now that I see the knob up close in this photo, it reminds me I gotta wipe it down better. When done properly there won't be any white outside the letters.)