Learn Portuguese (Portugal): O aluno é louro.

Because Portuguese requires gender agreement, the article, noun, and adjective all change to match. You would say A aluna é loura. Notice how the endings change to an -a for a feminine subject.

Why do we use é here instead of está?

The verb é comes from ser, which is used for permanent or defining characteristics. Physical traits like natural hair color fall into this category. You use estar (like está) for temporary conditions, like being tired or sick.

I've also seen the word loiro. Is that the same as louro?

Yes! Both louro and loiro are correct and mean the exact same thing. You will hear both used in Portugal, so it is just a matter of personal preference.

If I just wanted to say 'the blond student' without the verb, what is the word order?

In Portuguese, adjectives generally come after the noun they describe. So 'the blond student' translates to o aluno louro, rather than putting the adjective first like in English.