Since colored wire frames are now in Blender 2.80 here is an Addon that can do a couple of things:
- select a multiple objects and give them a random color
- select multiple objects and give all of them the same color
- select multiple objects and give them a random range of colors
- change wire color to Viewport Display color in Material
The last one is useful if you want to differentiate between groups of objects but also among each other.
For example you might want all plants to be green. But you dont want all plants to be the same type of green but different shades of green.
Here is a short video explaining it: