Many of the over-the-counter tests (including Ancestry, 23 & Me, and Family Tree) will test for a few of the most common variants on the MC1R gene. The vast majority of these tests only include three of the most common variants. They do not test for all known variants and do not fully sequence the MC1R gene. These testing companies are attempting to infer a phenotype (what you look like) from a very limited data set. Since they do not test for all known variants, they are often wrong at determining whether someone has red hair.