"They do not like red apples."
Translation:Ils n'aiment pas les pommes rouges.
Why 'les pommes rouges' and not 'des pommes rouges'? I can never get this figured out - I just guess and get it wrong more often than right.
You've forgotten about the exception that the object of verbs of preference (aimer, detester, préférer, etc.) must use the definite article. When you see those kinds of verbs, the definite article should always trigger your memory.
And by the way only indefinite (un, une) and partitive (du, de la) articles change to "de" in the negative. The definite article (le, la, les) does not change in negative statements.