ah ok, so if you want grab the set-LED messages then listen to /grid/led/set which also has three arguments, and is, of course, also on the serialosc reference page.
if you want to know all the commands used by serialosc, look at the reference page, Jason’s first link. there is nothing else to know about serialosc message formats and the reference page is clearly written.
if you have more general questions about OSC, then go to Jason’s second link.