Shameless plug: I have written an hexadecmial editor (in Rust) that colors bytes. It looks similar to hexyl.

https://github.com/0xfalafel/hextazy

Some nice features are:

- robust undo

- insertions (not just overwriting)

- inspect the value of selected bytes

- search

I have also recently discover this other project that is pretty cool: https://github.com/mentebinaria/dz6