hexyl is a hex viewer for the terminal. It uses a colored output to distinguish different categories of bytes (NULL bytes, printable ASCII characters, ... README.md · Issues 18 · Pull requests 6
You can use the xxd command to transform a file in Vim to hex representation, doing :%!xxd : enters command-line mode, % matches whole file as a range.
The hexedit command provides a way to edit binary files, but to view and save the content in a file for later analysis without editing, try the xxd command.