The Voyager app does not show it. When selecting to view the sidebar it shows a different image instead - the Lemmy mouse thing, but no colorful logo.

well, it’s a Lemmy App, so that makes sense it shows a stylised Lemming, that it should show Lemmy Kilmiester is another debate entirely :)

They

https://joinfediverse.wiki/Apps

all sit on top of the ActivityPub protocol and are a subset of the federated universe (FediVerse) of applications.