"The combination of yellow and pink makes this wall very interesting."
Translation:Die Kombination von Gelb und Pink macht diese Wand sehr interessant.
Would "gelb" and "pink" be capitalised in this case, or are they adjectives of "Kombination"?
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.
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.