A person in a large pink triangle-shaped costume waves as a man and a woman dressed in matching brightly-colored striped and polka-dotted outfits smile back.
The person is marching in a parade.
The person indicated could be any of three people; the first person mentioned or either the man or woman in the matching costumes.
Waving isn't the same as marching. Wearing costumes doesn't mean you're in a parade.
The person may not necessarily be marching in a parade even though they are dressed in a costume.