"The outfit is yours."
Translation:O traje é seu.
seu/sua is for ele, ela, or você. teu/tua is only for tu. Você in portugal is formal, tu informal. in brasil we don't care. in some places they only use tu, in some places they only use você, and in some places we mix the two. there is no distinction, just whatever you want to use and where you live. "o senhor" and "a senhora" are formal in brasil. você and tu had no informal or formal distinction
Rachel: Your question has to do with the "formal" and "informal" forms. The reason for your confusion is that the informal forms don't exist in English, anymore. But they used to, i.e. "thy and thine". Fortunately, from the discussion below, I see that the informal forms are not commonly used.
From what I understand about the gender of possessive adjectives, such as SEU/SUA, is that they refer to the noun they are modifying. For instance "o frango é seu" could mean both "the chicken is HIS or HERS". "seu" is used in this case because "o frango" is masculine and does not change with the gender of the chicken's owner.
The word Você seems similar in many respects with Usted in Spanish. It is a formal address form of 'You' which is used in the third person (just like 'him', 'her', or 'it'). As such it has agreement with sua / seu for feminine / masculine forms of words. So when talking to someone you know well it's okay to use tua carta for example, it might be better to say sua carta when speaking to someone formally, thereby implying Você.
Roupa=clothes/ traje=outfit. Clothes is like shirt and pants, outfit is more vast like hat glasses and scarves. You could say eu gosto de suas roupas and mean the same thing basically but it's not really correct and doesn't nessesarely imply what the person is currently wearing or in the case of o traje é seu, a roupa é sua wouldn't specify the outfit layed out, basically traje is more specific than roupa like I like what you currently choose to wear vs I like all you have as an option to wear
The gender reflects the noun, not the person. Seu/Sua applies to ele, ela and você (him, her and you). Teu/tua applies to the more intimate/formal tú (you). O traje é teu should be acceptable in this case as it is also a valid response. However, in Brasil, it is rare that people use the Tú form of anything. Você should always be your default answer unless tú is specifically stated. Even in the south where it is common to hear tú/teu/tua, they still use the conjugation for você.