Here is an Idaho freeway entrance sign post. This is at Exit 52 (Arbon Valley Road) in south east Idaho.
Notice the non lettered Interstate shields (Idaho uses very few of the lettered variety) and the dark green paint, like California. Unlike California, Idaho doesn't use button copy.
Here's US 93 at Idaho 74, south of Twin Falls.
Note the brown US30 scenic route sign.
I15 business route signage.
This is Exit 44 (Jensen Road) off I15.
This is the same place, stand alone sign.