"The combination of yellow and pink makes this wall very interesting."
Translation:Die Kombination von Gelb und Pink macht diese Wand sehr interessant.
Why is Kombination correct but Verbindung not? The rollover hint lists both.
Because it's not "the yellow" or "the pink" but simply "yellow and pink" -- no definite article.
der is the genitive case of the definite article.
Would "gelb" and "pink" be capitalised in this case, or are they adjectives of "Kombination"?
I think they should be capitalised -- you're talking about the colours themselves.
I agree with mizinamo: it makes sense to capitalize them because they are used as nouns in this sentence.
In fact, that's one of my favorite rules: German Orthography Rule 72! "Wie Substantive gebrauchte Adjektive und Partizipien werden in der Regel großgeschrieben." (Translation: "Adjectives and participles used as nouns are generally capitalized.") Duden even provides these examples of colors used as nouns: das Blau des Himmels; in Blau und Gelb.
I was expecting "macht" to be "machen" since we're speaking of "Gelb und Pink" which makes a plural context
The subject is not Gelb und Pink but rather die Kombination aus Gelb und Pink -- a noun phrase headed by the noun Kombination which is singular.
Because in a regular statement, the inflected verb is the second thing in the sentence, not the last thing.
Here, the inflected verb is macht; it is third person singular because the subject is Die Kombination von Gelb und Pink, a single idea.
The verb stands directly after that subject and is thus the second thing in the sentence.