El actor colombiano habla español.

Because actor is a singular countable noun, and in Spanish you normally need an article or another determiner with it.

• El actor colombiano... = the Colombian actor...
• Un actor colombiano... = a Colombian actor...

Leaving out el here would sound unnatural in normal Spanish.

In Spanish, descriptive adjectives usually come after the noun.

So:

• el actor colombiano = the Colombian actor

This is the normal word order. Putting colombiano before the noun is not the usual neutral pattern.

In Spanish, words for nationalities are normally written in lowercase.

So you write:

• colombiano
• español
• inglés
• francés

This is different from English, where Colombian and Spanish are capitalized.

For the same reason: in Spanish, languages are also usually written in lowercase.

So:

• Habla español
• Estudio alemán
• El francés es difícil

Only proper names are capitalized, not language names in normal usage.

Habla is the third-person singular present tense form of hablar.

From the verb:

• yo hablo = I speak
• tú hablas = you speak
• él/ella/usted habla = he/she/you speak

So in this sentence, habla means he speaks, because the subject is el actor colombiano.

After hablar, Spanish normally uses the name of the language without an article.

So you say:

• Habla español
• Hablo inglés
• Hablan italiano

But the article can appear in other kinds of sentences:

• El español es interesante.
• Me gusta el español de Colombia.

So the lack of el here is completely normal.

A few useful pronunciation points:

• h in Spanish is silent, so habla sounds roughly like AB-la
• ñ in español sounds like ny in canyon
• español sounds roughly like es-pan-YOL

Also, the stress is:

• HAB-la
• es-pa-ÑOL
• co-lom-bia-NO

Yes. In this sentence, actor is masculine.

The feminine form is:

• la actriz colombiana habla español

Notice that several words change to match the feminine noun:

• el → la
• actor → actriz
• colombiano → colombiana

This is called agreement.

Yes, especially in Spain, castellano is also a common word for the Spanish language.

So you may hear both:

• Habla español
• Habla castellano

Both are correct, though español is the most widely understood general term for learners. In Spain, castellano can sometimes emphasize Castilian Spanish or distinguish it from other languages spoken in Spain.

Normally, it means in general: it describes his ability or usual language use.

• El actor colombiano habla español. = he speaks Spanish

If you want to stress that he is speaking it right now, Spanish often uses the progressive:

• El actor colombiano está hablando español.

So the simple present here is best understood as a general fact.