Learn French: Les étoiles multicolores illuminent le ciel, qui n'est plus noir. - The multicolored stars illuminate the sky, which is no longer black.

You can just add Comme, Que, or Ce que to the beginning of the statement! For example: Comme les étoiles illuminent le ciel ! In French, you do not invert the subject and verb for this kind of exclamation; you keep the normal declarative word order.

Why is the relative pronoun qui used here instead of que?

Here, qui translates to 'which' and acts as the subject of the verb est. You must use qui for subjects, whether they are people or things. You would only use que if it were the direct object of the following verb (for example: le ciel que je vois - 'the sky that I see').

Why does the adjective multicolores take an s? Aren't compound color adjectives supposed to be invariable?

Although it contains multiple parts, multicolore is treated as a single, regular descriptive adjective in French, not a compound color adjective like bleu clair. Therefore, it follows the normal rules of agreement and takes an s to match the plural noun étoiles.

Can you remind me how the negative structure ne ... plus works in this sentence?