Technically it is never stated if the character of Ford Prefect is white, black or any other color. It is generally assumed that he appears to be white. Though his only real physical description says that he has ginger hair and smiles a bit too wide. However, we can assume he is white because having ginger hair is more commonly associated with fair skin. Being an alien, his Earthbound nationality is neither established or relevant.
Taste is highly subjective. Though it seems that people who are already fans of Douglas Adams seem to enjoy the movie more than those who have no previous exposure to this series. On the other hand, many of the movie's jokes are taken directly from the books, so they do not necessarily work on the big screen when you already read the punchlines.
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