You can have any color you want, as long as it's black? What does that mean?

I've seen this a couple of times in places. I know Henry Ford said, but what exactly does it mean?

It means that you won't be going to a good university.

They only made them in black, So what they are saying is you have no choice

Ford's early production line only made cars that were painted black.
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Ford was referring to the trade-off between having a product and that product being affordable. At the time he first started mass manufacturing cars, all cars were hand-made and could only be bought by the very wealthy. The first model A was produced in 1908 and didn't require expensive servicing. By the way - it was blue!