Why is the correct form “qui est” and not “qu’est”? My understanding was that vowels contract and are replaced with an apostrophe? Is there a rule for when we use contractions?

Are there rules for descriptors like colors — when to use "orange" rather than "roux" — or is it the equivalent of saying ginger or redhead in English?

Apologies, but I don’t understand the part about the pronouns!

How do we know when to say something like “Elle te rend visite” rather than “Elle visite toi”? In this instance, you've explained the context (one is to visit a friend, one is to visit someone in a specific context) but in other contexts, how do we know when we'd use the "neutral object" pronouns instead of the the lui/moi/elle etc.?

How do we know when to use "pour" instead of "de"? And the additional "de" before "la nourriture" has confused me further...

That is so adorable!

I was trying to anthropomorphize the animal — “cute little man” — but I don't know if that's common in French, haha! Calling him a lil' cabbage is so sweet, though!

A few answers to your questions:

1) "Que" can be contracted, "qui" cannot (it sometimes happen in the spoken/colloquial language but it's not standard French). Here, you need a subject relative pronoun, so that would be "qui", not "que".

2) People are definitely "roux", and so are animals, ex "un renard roux" (nobody would say "un renard orange"). "Un chat orange" definitely sounds less noble. "Roux" theorically encompasses colors ranging from carrot orange to copper and red, so don't hesitate to use it. Things like carrots are "orange".

3) As I mentioned, the emphatic pronouns (which can be subjects or objects) are used when emphasizing the pronoun and after prepositions. Ex: « MOI, je parle anglais » (implying: you don't, he/she doesn't etc), « je veux aller en ville avec TOI »
They are also used in some nominal sentences, ex « mon frère pardonne facilement, MOI pas » ("my brother easily forgives — I don't)
So, in a neutral sentence, it would be => Elle TE visite

4) This would be too long to explain, but generally, "pour" is used to indicate the purpose of something, just like "à". However, it's not common at all: in most cases, you'll find "de" or "à". Really, no need to overthink it.

5) In this case, you can say "c'est UN petit bout de chou" ("un bout de chou" is especially used for babies). The most common terms to anthropomorphize animals are "fifille" (for females) and "pépère" (for males), both of which are terms of endearment based on "fille" and "père", respectively.

Merci beaucoup pour votre temps! (and your help, too)