Well, once in browser, all is simple: you can give it a name and make the header of the page a distinctive color.
But you have to get there, and this requires some configuration in Raspbian and a bit in OctoPrint.
I'll prepare a short guide in a couple of days and post it here. The basic idea is to use the USB device identification codes (usually stored in the EEPROM, e.g. for a FTDI FT232RL) and map the code to a particular name for each printer. Then the name is used to configure the http daemon of OctoPrint.
L.E. Here is a config guide for multiple printers on OctoPrint/RPi, pretty long,