El chaleco reflectante es verde.

Because chaleco is a masculine noun in Spanish, so it takes the masculine singular article el.

A good thing to remember is that noun gender in Spanish is a grammatical category, not usually about biological sex. A vest is just grammatically masculine, so you say:

• el chaleco
• un chaleco

If you make it plural, it becomes:

• los chalecos

Spanish normally uses ser for inherent or identifying characteristics, and color is usually treated that way. So:

• El chaleco es verde. = The vest is green.

Using estar with color is uncommon in a basic descriptive sentence like this. For learners, the safest rule is:

• use ser for what something is
• use estar for how something is in a temporary state or where it is

So color normally goes with ser.

In Spanish, most descriptive adjectives usually come after the noun. So:

• chaleco reflectante = reflective vest
• coche rojo = red car
• casa grande = big house

Putting an adjective before the noun is sometimes possible, but it often changes the tone, emphasis, or meaning. In normal everyday Spanish, chaleco reflectante is the natural order.

No. Reflectante is one of many adjectives that has the same form for masculine and feminine in the singular.

So you can say:

• el chaleco reflectante
• la chaqueta reflectante

It does change for number, though:

• el chaleco reflectante
• los chalecos reflectantes

So the plural adds -s: reflectantes.

Verde is an adjective that has the same form for masculine and feminine singular:

• el chaleco verde
• la camisa verde

But it does change in the plural:

• el chaleco verde
• los chalecos verdes
• la camisa verde
• las camisas verdes

So verde agrees in number, but not in gender.

Not in normal Spanish. That sounds unnatural.

The standard order is:

• El chaleco reflectante es verde.

If you want both adjectives after the noun, that is normal:

• El chaleco reflectante verde...

But in your sentence, verde is not inside the noun phrase. It comes after es, because it is the predicate adjective:

• El chaleco reflectante = the reflective vest
• es verde = is green

So the sentence is built like:

subject + verb + adjective

A simple Latin American-style pronunciation guide would be:

• chaleco ≈ cha-LE-ko
• reflectante ≈ re-flek-TAN-te
• es ≈ es
• verde ≈ BER-de or VER-de depending on how strongly the v and b sound blend in your accent

A few helpful notes:

• ch sounds like English ch in chair
• c before a, o, u sounds like k
• r in verde is a light tap, not a strong English r
• stress falls naturally on:
  • chaLEco
  • reflecTANte
  • VERde

Yes, chaleco reflectante is a natural and widely understandable term.

Depending on the country or context, you may also hear things like:

• chaleco de seguridad
• chaleco reflectivo

But chaleco reflectante is clear and standard enough for learners, and people across Latin America will understand it.

Because Spanish does not use an extra word between ser and an adjective.

In English, you say:

• The vest is green.

In Spanish, the structure is simply:

• El chaleco es verde.

No extra word is needed. The adjective verde directly describes the subject after es.

Normally, no. In a full sentence like this, you usually need the article:

• El chaleco reflectante es verde.

Leaving out el would sound incomplete in most contexts.

Spanish often uses articles where English sometimes does not. So when you mean the reflective vest, you should include el.

The plural is:

Los chalecos reflectantes son verdes.

Here is what changes:

• el → los
• chaleco → chalecos
• reflectante → reflectantes
• es → son
• verde → verdes

This is a good example of agreement in Spanish: articles, nouns, and adjectives all have to match in number.