That's right: From June 3 to July 2, there'll be a post each day highlighting Teenage Mutant Ninja Turtles canon immigrants. Now, because TMNT canon is a little confusing, it can be hard to tell what counts as a canon immigrant and what doesn't. So for the purposes of this blog, a TMNT canon immigrant is anything (a) from the movies, cartoons, video games, toy lines, or tie-in comic series that later appeared in (b) TMNT volumes 1, 2, or 4 [because they're by the original creators] or TMNT volume 5 [because the original creators are involved, it's the new official continuity, and its goal is to use as much of the diverse TMNT lore as possible].
In the 80s cartoon, the Foot Clan's symbol was a red human footprint, like so:
But in the 2003 series, the symbol was changed to be a three-toed dragon footprint:
The IDW series splits the difference. As we see in Teenage Mutant Ninja Turtles: The Secret History of the Foot Clan #1 (January 2013) (as an example; I don't know if these are the actual first appearances of these symbols), the feudal-era Foot Clan uses the human footprint...
...while the current Foot Clan uses the dragon one.