Ya no me pruebo ropa negra; he vuelto a usar colores verdes y rojos.

Ya no means no longer / not anymore. It usually goes before the verb phrase: Ya no me pruebo... You can also place ya after the verb for emphasis or style: No me pruebo ya ropa negra, which is still correct, though Ya no... is the most neutral.

Contrast:

• ya = already / now: Ya uso colores.
• todavía no = not yet: Todavía no uso colores.

Because probarse is the verb used for trying on clothes. It’s reflexive: you’re trying the clothes on yourself.

• Me pruebo ropa = I try clothes on.
• Pruebo ropa = I test/try the clothes (as objects), not try them on.

Related:

• probar (non‑reflexive) = to taste/try/test: Probar el vino.
• In Spain, probar a + infinitive = try to (attempt): Prueba a llamar más tarde.

With a conjugated verb, the pronoun goes before: Me pruebo.
With an infinitive or gerund, you can attach it or put it before the helper:

• Quiero probarme esta chaqueta. / Me quiero probar esta chaqueta.
• Estoy probándome la camisa. / Me estoy probando la camisa. Commands:
• Affirmative: Pruébate esto.
• Negative: No te pruebes eso.

Ropa is a mass noun in Spanish; it normally stays singular when referring to clothing in general. You only pluralize when using a countable word:

• General: ropa negra (black clothing)
• Countable: prendas negras or prendas de ropa negras (black garments)

The plural ropas exists but is rare and sounds marked/literary or regional; avoid it in standard usage.

Adjectives agree in gender and number with the noun they modify.

• ropa is singular feminine → ropa negra
• colores is plural masculine → colores verdes y rojos

Note: color is masculine: el color rojo, los colores rojos (never rojas).

With a plural noun, the adjectives should also be plural: colores verdes y rojos is the regular form.
If you want to treat the color names as nouns, rephrase: el verde y el rojo (no need for colores):

• He vuelto a usar el verde y el rojo.
• Or drop the articles in informal speech: He vuelto a usar verde y rojo.

Usar is correct, but in Spain llevar is often more idiomatic for “wear”:

• He vuelto a llevar colores verdes y rojos. (I’m wearing them again.)

Other options:

• ponerse = to put on: Me he vuelto a poner ropa verde.
• vestir/vestirse (slightly more formal): Vuelvo a vestirme de verde.
• ir de + color (set phrases): Voy de negro.

Volver a + infinitive means to do something again / to go back to doing it.

• Vuelvo a usar = I’m using again (right now/as a habit starting again)
• He vuelto a usar = I have started using again (recent change with present relevance)
• Volví a usar = I used again (completed past event)

The semicolon neatly separates two related independent clauses. Alternatives:

• Period: Ya no me pruebo ropa negra. He vuelto a usar...
• Connector: Ya no me pruebo ropa negra, pero he vuelto a usar... (but)
• You can use sino que after a negation to oppose/replace the first idea:
  Ya no me pruebo ropa negra, sino que he vuelto a usar colores...
  Avoid a simple comma between two independent clauses with no connector.

No article is used when speaking generally/indefinitely:

• (No) me pruebo ropa negra = black clothing in general.
• usar colores = colors in general.

Use articles for specific, known items:

• No me pruebo la ropa negra = not trying on the specific black clothes.
• He vuelto a usar los colores verde y rojo (in a technical/contextual sense, e.g., design talk).

It already implies “not any.” Spanish doesn’t require an extra word. If you want to be explicit or stronger, you can say:

• Ya no me pruebo ninguna prenda negra.

For plural feminine clothes (las), with a reflexive subject:

• Me las he vuelto a probar. (I’ve tried them on again.)
• Me las volví a probar. (I tried them on again, completed past.) Pronoun order with compound tenses: reflexive/objects go before the auxiliary: Me las he...
  With an infinitive, you can attach: He vuelto a probármelas. / Me las he vuelto a probar. Both are correct.