Compro un boleto rosado.

Compro is the first-person singular present indicative form of comprar.

So:

• comprar = to buy
• compro = I buy / I am buying

Spanish often uses the simple present where English might use either I buy or I’m buying, depending on context.

Spanish often leaves out subject pronouns because the verb ending already shows who the subject is.

Here, compro already tells you the subject is I. So Compro un boleto rosado is completely natural.

You could say Yo compro un boleto rosado, but adding yo usually gives extra emphasis, contrast, or clarity:

• Yo compro un boleto rosado, no uno azul. = I’m buying a pink ticket, not a blue one.

Because boleto is a masculine singular noun.

In Spanish, articles must match the noun’s gender and number:

• un boleto = a ticket
• unos boletos = some tickets

If the noun were feminine, you would use una instead.

In much of Latin America, boleto commonly means ticket.

Depending on the country and the situation, related words can also be used:

• boleto = ticket, fare ticket, pass, sometimes lottery ticket
• entrada = admission ticket, especially for an event
• billete = in many places, mainly banknote or bill, though in some regions it can also mean ticket

So boleto is a very normal Latin American word here.

In Spanish, adjectives usually come after the noun.

So:

• un boleto rosado = a pink ticket

This is the normal word order. English usually puts the adjective before the noun, but Spanish commonly does the opposite.

With color adjectives especially, placing the adjective after the noun is the standard pattern.

Because adjectives usually agree with the noun in gender and number.

Since boleto is masculine singular, the adjective is also masculine singular:

• boleto rosado

If the noun were feminine, the adjective would change:

• entrada rosada

If it were plural:

• boletos rosados
• entradas rosadas

Yes, in many cases you can.

Both can refer to the color pink, but they are used a little differently:

• rosado / rosada behaves like a regular adjective and changes form
• rosa is often used as a color word that stays the same

Examples:

• un boleto rosado
• un boleto rosa
• una entrada rosada
• una entrada rosa

Both are understandable. In many Latin American contexts, rosado sounds very natural.

It can mean either one, depending on context.

Spanish simple present often covers both:

• I buy a pink ticket (habitual or general)
• I’m buying a pink ticket (right now or in the current situation)

If you want to strongly emphasize that the action is happening right now, Spanish can also use the present progressive:

• Estoy comprando un boleto rosado.

But Compro un boleto rosado is still perfectly possible in context.

Yes, but Compro un boleto rosado is the most neutral and natural order.

Spanish word order is somewhat flexible, but changes usually add emphasis or sound less neutral:

• Yo compro un boleto rosado. = emphasizes I
• Un boleto rosado compro. = unusual in normal conversation; sounds marked or poetic

So for a basic statement, Compro un boleto rosado is the best standard form.