From: The Subjectivity of Wine:

In 2001, Frederic Brochet, of the University of Bordeaux, conducted two separate and very mischievous experiments. In the first test, Brochet invited 57 wine experts and asked them to give their impressions of what looked like two glasses of red and white wine. The wines were actually the same white wine, one of which had been tinted red with food coloring. But that didn’t stop the experts from describing the “red” wine in language typically used to describe red wines. One expert praised its “jamminess,” while another enjoyed its “crushed red fruit.” Not a single one noticed it was actually a white wine.

As the author puts it: So much for objectivity…

For more info see: How Winemaking Works and Wine basics