Jozijoe, some more reading for you.
Mendels law of genetics.
I agree with you that the so called coloured race was a handy catchall classification for the idiots who ran SA from 1948 to 1994.
I am also aware that a large slice of the "coloured" population has a very large Malay gene pool.
in fact most SA families who have been in SA since the 1700's (such as mine) have Black or Malay Ancestry mixed in with the European genes.
but if you happened to read before putting both feet into your mouth, go and check what Colour the offspring will be if both parents have Black genes in their Ancestry.
Then read up on Mendels law and give us an idea of what the spread would be if the Coloured Couple both came from coloured parents and had 3 children.

In the same way your Fantasy idea of lets say a Black Womans egg with sperm from a white donor would still create divisions
AA,Aa and aa.
you would still end up all white looking children, all black looking children and coloured Children.
And seeing as you cant get colour or race out of SA's minds
it will continue.
Now lets tackle the next subject.