The salesperson shook his head and said "No, we don't sell to blondes".
So, the blonde left and came back with her hair dyed brown and said "I'll take that TV".
Again, the salesman said "No, we don't sell to blondes".
So she left again and came back with her hair dyed black and said "I want that TV".
But the salesman still said "No, we don't sell to blondes".
Finally, the blonde got fed up and said "That's it! How'd you know I was a blonde?!"
The salesman answered
Spoiler: