"Su perro es negro."
Translation:His dog is black.
In the lesson Su was translated as "his" and not "their" are they one in the same? This one confused me.
Can anyone explain why colours seem to have a plural form in some instances? Is it if you're referring to more than one item?
Yes. If a colour acts as an adjective, it has to match both the gender and the number of nouns it's modifying.
Because that is the way some people are. My explanation is correct, though. You can still trust it, believe me.