No m'agrada el negre; jo prefereixo el blanc.

Because Catalan agradar works differently from English to like.

In Catalan, the thing that is liked is the grammatical subject, and the person who experiences the liking is shown with an indirect object pronoun.

So:

• No m'agrada el negre literally works like Black is not pleasing to me
• m' = to me
• agrada = is pleasing
• el negre = black / the color black

This is why Catalan does not use a structure like I like black word-for-word.

m' is the shortened form of em, the weak pronoun meaning to me.

Before a verb beginning with a vowel, em becomes m':

• m'agrada
• m'estima
• m'interessa

Before a consonant, you normally keep the full form:

• em molesta
• em sembla

So m'agrada is just em agrada contracted for sound and spelling.

Because the verb agrees with el negre, not with me.

Here, el negre is singular, so the verb is singular:

• M'agrada el negre = I like black

If the thing liked were plural, the verb would be plural too:

• M'agraden els colors foscos = I like dark colors

This is one of the most important things to remember with agradar: the verb agrees with the thing liked.

Because here the colors are being used as nouns, not just as adjectives.

So:

• el negre = black / the color black
• el blanc = white / the color white

Catalan often uses the definite article when talking about colors as concepts in this way. You can think of it as a shortened version of:

• el color negre
• el color blanc

In this sentence, they function as nouns.

That is why they can stand on their own after el:

• el negre
• el blanc

But the same words can also be adjectives:

• el cotxe negre = the black car
• la camisa blanca = the white shirt

Notice that as adjectives they agree in gender and number:

• negre / negra / negres
• blanc / blanca / blancs / blanques

That is correct: Catalan often leaves out subject pronouns because the verb ending already shows the person.

So you could simply say:

• No m'agrada el negre; prefereixo el blanc.

The pronoun jo is included here for emphasis or contrast. It gives the feeling of:

• As for me, I prefer white
• I prefer white

So jo is optional, but it adds a bit of personal contrast.

Prefereixo is the first-person singular present form of preferir, meaning to prefer.

So:

• jo prefereixo = I prefer

This verb belongs to a group of Catalan -ir verbs that often insert -eix- in some present-tense forms:

• prefereixo
• prefereixes
• prefereix
• preferim
• preferiu
• prefereixen

So the -eix- in prefereixo is normal and expected.

It depends on context, but in this sentence it most naturally means the color black.

Because it is paired with el blanc, the sentence is clearly contrasting two colors:

• No m'agrada el negre; jo prefereixo el blanc.

In another context, el negre could mean the black one:

• Agafa el negre, no el blau = Take the black one, not the blue one

So the form is the same, and context tells you which meaning is intended.

Yes. Negre is the standard everyday Catalan word for the color black.

In this sentence, it is completely ordinary and neutral because it is simply naming a color.

As in many languages, words can have different implications depending on context, but here there is nothing unusual: it just means black.

The semicolon is not strictly necessary. It is just a punctuation choice that links two closely related ideas.

You could also write:

• No m'agrada el negre. Prefereixo el blanc.
• No m'agrada el negre, prefereixo el blanc.

You could also make the wording slightly fuller:

• No m'agrada el color negre; prefereixo el color blanc.

The original version is natural and concise, and the semicolon gives it a neat contrast between the two preferences.