Perhaps the most surprising thing about President Trump's vision for his southern border wall is the fact that he doesn't want to paint it gold.

Instead, he wants it to be painted "flat black," thinking that if it absorbs heat in the summer, migrants will not be able to climb it, current and former administration officials told The Washington Post on Thursday. Trump has been very vocal about how the wall should look, they said, down to the most mundane details; he even used to call former Homeland Security Secretary Kirstjen Nielsen early in the morning, waking her up, in order to discuss the barrier.

The wall, it had been decided, will actually be a steel bollard fence, with a special, secret material inserted in the hollow cavity to make it harder to cut, the officials said. Customs and Border Protection determined that the optimal height is between 15 and 18 feet tall, but Trump wants it to be 30 feet, the Post reports, with pointed tips rather than round ones. Trump also thinks the plans show too many gates in the barrier, and he wants smaller openings.

All of the changes are adding up, the officials said, and Trump has been warned about the rising cost, especially if the fence is painted black. "Once you paint it, you always have to paint it," one official said. Trump often brings the project up during unrelated meetings, the Post reports, and he has been reveling in "describing in graphic terms the potential injuries that border crossers might receive." Read more about Trump's dream wall at The Washington Post. Catherine Garcia