Battlers have their own specific rules, so it is best to ask the battler if he or she allows shiny legendaries.
However, do keep in mind that if your Shiny Manaphy does not have the location "Link Trade," then it is most likely hacked... Except for a select few events (Milotic, Pichu, etc), Wonder Card events are set as non shiny (although if the Manaphy egg is traded to another file, it has a chance of being shiny, hence, Link Trade). :(
I hope that answers your question because this does not belong here. ^^
Closed~