@Canoob, I have not used can-utils myself, so my help only goes so far.
I took a look at the GitHub repository for can-utils, and I did not see anything to explain the a and e parameters. I am not sure if they are supposed to be values for the colour setting, or if they were meant to be parameters. Could those be the parameters for a different can-utility?
@jvanier, Can you take a look at this please?
Note that cansniffer is for searching for differences in the CAN messages, so you will not see all the messages, just the messages that changed due to some event.
If you want to verify that you are receiving CAN messages and want to see all of them, then candump might be the utility you want.