humm, Thanks! I've got it! I'm brazilian and in portuguese "Portare" and "vestire" are the same thing in this context. I think i just misunderstood! :)
Viola, meaning the color, doesn't have different endings, maybe because it's really a noun, the name of the flower. Rosa is similar.
Yet rosso, nero, giallo and azzurro do have different endings. So why are the 'colours named after flowers' special?
Is there a difference between "Lei porta un vestito viola" and "Lei indossa un vestito viola" ? Portare and indossare?
The main mining of "portare" is "to bring", "to carry". The first thing I thought of when I saw this sentence was "she carries a purple dress". The meaning of "being dressed" is not so common. "Indossare un vestito" sounds more natural.
How can we tell whether she 'wears' a dress or if she 'brings' a dress? E.g. If a friend says to you, 'Porta un vestito viola!' how do you know if they mean to wear it to their house or to bring for later (maybe for going out later)?