You will need to create the file. The way I was able to do it was to get a link from uploading it to my google drive, then convert that link into a direct file link. There is a tool online that will change your shared link into a direct link.
From what I can tell from the patch notes, it has to be put in the dynamic config. I have been unsuccessful trying to get the dynamic color set to work though. I'm hoping they put out more information on this, as I would like to have custom color sets across my server.
I have the following in my dynamic config:
ActiveEventColors=custom
DynamicColorset=Cyan,Yellow,Blue,Green
I used those colors just for testing purposes because they stick out, but have not been able to get it to work. They don't really explain it well. When I setup an event in my startup file, it only puts those event colors and not my custom ones. I have a few more things to try and will post back if i'm successful.