Mi hermano se puso un traje azul y una corbata gris para la entrevista.

Because ponerse means to put on oneself / to get dressed in something, while poner by itself usually means to put / place something somewhere.

So:

• puso = he/she put
• se puso = he/she put on

In this sentence, se is the reflexive pronoun, showing that your brother is putting the clothes on himself.

• Mi hermano se puso un traje = My brother put on a suit
• Mi hermano puso un traje en la cama = My brother put a suit on the bed

It is the preterite tense of ponerse.

The preterite is used for a completed action in the past, which fits here because putting on the suit and tie is seen as a finished action before the interview.

Conjugation here:

• yo me puse
• tú te pusiste
• él/ella se puso
• nosotros nos pusimos
• vosotros os pusisteis
• ellos/ellas se pusieron

So se puso means he put on.

In Spanish, possessive words like mi, tu, su, nuestro usually replace the article.

So Spanish says:

• mi hermano = my brother
• tu casa = your house

Not:

• el mi hermano

This is different from English only in structure, not meaning.

Because Spanish nouns have grammatical gender.

• traje is masculine, so it takes un
• corbata is feminine, so it takes una

So:

• un traje azul
• una corbata gris

The article has to match the noun’s gender.

In Spanish, adjectives usually come after the noun, unlike in English.

So:

• a blue suit → un traje azul
• a grey tie → una corbata gris

That is the normal word order in Spanish.

Spanish adjectives often agree with the noun in gender and number, but not all adjectives change in the same way.

• azul stays azul in both masculine and feminine singular:

  • traje azul
  • camisa azul

• gris also stays the same in masculine and feminine singular:

  • traje gris
  • corbata gris

They do change in the plural:

• trajes azules
• corbatas grises

So in this sentence, both color adjectives stay the same because the nouns are singular.

Because azul and gris are adjectives describing the nouns, not separate nouns themselves.

The structure is:

• un traje azul = a blue suit
• una corbata gris = a grey tie

You only need the article before the noun:

• un traje
• una corbata

Here para means for, expressing purpose or intended use.

• para la entrevista = for the interview

It tells us why he got dressed that way.

Por would not be the natural choice here. Por often expresses ideas like because of, through, by, or around depending on context.

So:

• Se puso un traje para la entrevista = He put on a suit for the interview.

Because entrevista is a feminine noun, so it takes la in the singular.

• la entrevista = the interview

Also, in Spanish, when talking about a specific event already understood in context, using the definite article is very natural.

Yes, but the meaning changes slightly.

• se puso focuses on the action of putting on the clothes.
• llevó usually means wore / had on, focusing more on what he was wearing.
• vistió can mean dressed or wore, but it is less common in everyday speech for this exact idea.

Compare:

• Mi hermano se puso un traje azul... = My brother put on a blue suit...
• Mi hermano llevaba un traje azul... = My brother was wearing a blue suit...

So se puso is the best choice if you want the action of getting dressed.

Because y simply links the two clothing items:

• un traje azul y una corbata gris

The color adjectives belong to each noun individually:

• traje → azul
• corbata → gris

So the structure is:

• [noun + adjective] y [noun + adjective]

This is completely natural Spanish.

Yes. Ponerse is a very common verb with several meanings depending on context.

For example:

• ponerse ropa = to put on clothes
• ponerse triste = to become sad
• ponerse enfermo = to get sick
• ponerse de pie = to stand up

In this sentence, because it is followed by clothing items, the meaning is clearly put on.

Yes, it is very natural.

The basic order is:

• subject + reflexive pronoun + verb + object

So:

• Mi hermano = subject
• se = reflexive pronoun
• puso = verb
• un traje azul y una corbata gris = what he put on
• para la entrevista = purpose

This is standard, natural Spanish word order.