If client does not allow displaying +X Potion, you can do a hack: set reserved IDs for creator's name and return it from clif:
e.g.
999991 = +1
999992 = +2
...
it will make something like "+1's potion"
's you can easily hex out from client
You can't do it without client reverse engineering. Brainstorm's assumption is totally false, ^COLOR is option for Ragnarok's dialog parser, and \033[1;37 is only for console.
Client is unable to remove effects manually, you should do jump into current location. It refreshes player's client and the Others will not see effect after teleportation.