That was my thought as well. Plus, Red is used for the 5.0-5.9% range. Red is symbolic of danger, and 5.0-5.9% unemployment isn't great but it's not at the "red alert" level.
I would really like to see this map on a global scale.
Per your mention, red is definitely a warning affordance.
Now the places lower than 5%, I want to know why. There's something either insulating them or the coasts are the other extreme.
Also, I want to see this as the US pulls out of it. Will the coasts recover first and trickle back in? Or, will the healthy parts of the US grow outward?