Haar gezicht werd rood van de kou.

Haar gezicht means her face.

• haar is the possessive adjective her
• gezicht is the noun face
• Dutch does not use an article before a possessive in this kind of phrase, so het haar gezicht is wrong

So the structure is simply:

• haar gezicht = her face
• mijn gezicht = my face
• zijn gezicht = his face

gezichtje would mean little face or cute face, which changes the meaning and tone.

Werd is the past tense of worden, which usually means to become.

So:

• wordt rood = becomes red / turns red
• werd rood = became red / turned red

In this sentence, werd rood describes a change of state: her face was not red before, and then it turned red.

Because werd rood focuses on the change.

• Haar gezicht werd rood = her face turned red
• Haar gezicht was rood = her face was red

So:

• werd rood = the redness started or developed
• was rood = it was simply in that state

English makes the same distinction between turned red and was red.

No. Even though worden is often used to form the passive, here it is not passive.

Here, worden keeps its basic meaning to become:

• Het huis werd gebouwd = The house was built → passive
• Haar gezicht werd rood = Her face became red → not passive

A good test: if you can replace it with became, it is not passive.

Because rood comes after the verb and functions as a predicate adjective, not as an adjective directly before a noun.

Compare:

• een rood gezicht = a red face
  Here the adjective comes before the noun.
• haar gezicht werd rood = her face turned red
  Here the adjective comes after the verb.

After verbs like zijn, worden, blijven, adjectives normally stay in the basic form:

• Hij is moe
• De lucht werd grijs
• Het water blijft koud

So rood is correct.

Literally, it means from the cold.

In Dutch, van can be used to indicate the cause of a physical reaction:

• trillen van de kou = shiver from the cold
• rood worden van schaamte = turn red from shame
• huilen van het lachen = cry from laughing

So Haar gezicht werd rood van de kou means that the cold caused her face to turn red.

Yes, door de kou is also possible, but it sounds a bit different.

• van de kou often sounds more natural for a bodily reaction or state caused by something
• door de kou emphasizes the cause a bit more directly, like because of the cold

For this sentence, van de kou is very idiomatic and probably the most natural choice.

Because kou is usually used here as a noun meaning the cold.

Dutch often uses the article in expressions like this:

• van de kou = from the cold
• in de zon = in the sun
• uit de wind = out of the wind

Without the article, van kou would sound unnatural in standard Dutch.

The structure is:

• Haar gezicht = subject
• werd = finite verb
• rood = predicate adjective
• van de kou = prepositional phrase showing cause

So the sentence follows normal Dutch main-clause word order:

Subject + finite verb + rest

That gives:

Haar gezicht werd rood van de kou.

Yes, gezicht is a het word:

• het gezicht = the face

That matters for the article when the noun stands alone:

• het gezicht
• een gezicht

But in haar gezicht, there is no article, because the possessive haar replaces it.

So although gezicht is neuter, you do not see het in this sentence.

Sometimes, but not always.

• rood worden literally means to become red / turn red
• blozen means to blush

In this sentence, the reason is de kou, so blush is not the best translation, because in English blush is usually about embarrassment or emotion.

So here:

• rood worden = turn red
• not usually blush

Yes. That would mean her cheeks turned red.

Compare:

• Haar gezicht werd rood = her face turned red
• Haar wangen werden rood = her cheeks turned red

Notice the verb changes too:

• gezicht is singular → werd
• wangen is plural → werden

Both are natural, but wangen is often even more specific in this kind of context.

Werd is pronounced roughly like vert but with a w sound at the start.

A simple approximation for English speakers is:

• werd ≈ wert

A few notes:

• the w in Dutch is softer than English w, somewhere between English w and v
• the e is short, like in bed
• the final d is often pronounced like t at the end of a word

So in actual speech it may sound close to wert.