U.S. President Donald Trump's administration is once again touting black paint on border walls to deter illegal migration — a questionable and expensive proposition.

Homeland Security Secretary Kristi Noem says the entire southern border wall with Mexico is being painted black to deter illegal immigration, at President Trump's request.

U.S. Homeland Security Secretary Kristi Noem said the nation's southern border walls will be painted black to better repel anyone who might try to scale them.