El collar es azul.

In Spanish, it is very common to use the definite article with nouns when you mean the specific thing.

• el collar = the necklace
• collar by itself would usually sound incomplete in a basic sentence like this

So El collar es azul is the normal way to say The necklace is blue.

Because collar is a masculine noun in Spanish.

• el collar = the necklace
• la collar is incorrect

In Spanish, every noun has grammatical gender, and collar happens to be masculine, even though the object itself is not biologically male.

You usually learn a noun’s gender together with the noun itself:

• el collar
• not just collar

That said, there is no perfect rule you can always rely on. Many nouns ending in consonants can be either masculine or feminine, so the safest approach is to memorize the article along with the word.

Es means is.

It is the él/ella/usted form of the verb ser, which means to be.

So:

• ser = to be
• es = is

In this sentence:

• El collar es azul = The necklace is blue

Spanish has two main verbs for to be: ser and estar.

Here, ser is used because the sentence describes a basic characteristic of the necklace: its color.

• El collar es azul = The necklace is blue

Color is normally treated as an identifying or inherent quality, so ser is the standard choice.

In Spanish, adjectives often come after the noun, especially when they describe physical qualities like color.

So:

• el collar azul = the blue necklace
• El collar es azul = The necklace is blue

This is different from English, where adjectives usually come before the noun.

Some Spanish adjectives change form for gender, but azul usually does not.

Examples:

• el collar azul
• la camisa azul

Both use azul.

However, it does change in the plural:

• el collar azul
• los collares azules

So azul stays the same in singular masculine and singular feminine, but becomes azules in the plural.

No, that would not be normal Spanish.

The usual order is:

• el collar azul = the blue necklace

Spanish adjectives generally come after the noun, especially colors. Putting azul before collar would sound unnatural here.

A common Latin American pronunciation is roughly:

• el co-YAR es a-SOOL

A few details:

• ll in collar is often pronounced like y in yes in much of Latin America
• the stress in collar is on the last syllable: co-LLAR
• azul is stressed on the second syllable: a-ZUL

Exact pronunciation can vary by region, but that version will usually be understood.

Yes, sometimes you can, if the context makes it clear what you are talking about.

• Es azul = It is blue

Spanish often leaves out pronouns, and sometimes even a repeated noun, when the listener already knows the subject.

But if you are introducing the idea for the first time, El collar es azul is clearer.

You would make the article, noun, verb, and adjective plural:

• Los collares son azules.

Changes:

• el → los
• collar → collares
• es → son
• azul → azules

So Los collares son azules means The necklaces are blue.

For A necklace is blue, you would normally say:

• Un collar es azul.

If you mean The necklace is a blue one, Spanish usually still says:

• El collar es azul.

Spanish often does not need an extra word like one in this kind of sentence.