Note that the “-c -m 0.8” options are optional, you can simply start compton without args. The options can be defined in a ~/.config/compton.conf file and will likely be overridden by anything you specify in the command.
Yes, I should have made clear this was the case. To clarify, the -c applies a slight shadowing to the menus and panels and the -m 0.8 applies a slight transparency to the menus. That is to say, the opacity is set to 80%. You could, of course, decrease the menu opacity by decreasing the decimal value.
For my own part, I have found the conf file to be a bit flaky. Hence my preference to put the arguments directly in the command.