Something about the way that random colors are assigned to objects is a bit weird.
When I duplicate an object via ALT-D (Duplicate Linked) a new random color is assigned as it should be. However, when I duplicate an object via SHIFT-D (Duplicate Object), all the duplicated objects have the same color. It would be great is those duplicates have a random color as well.
Another weird thing happens when you duplicate object via SHIFT-D. Take a look at the example below. The center row has random colors for all the cubes. When I select all of them and duplicate them (SHIFT-D) at the same time, they have the same colors as the original object (boxes in the top row). However, if I duplicate each box individually, every box has the same color (bottom row). Even if I copy an orange cube, the copy will turn to green (in this example).
As you can imagine this is very confusing to work with. Somehow this logic seems reversed. I would rather expect a duplicate-linked object to keep the same color as the original and the one with is an independent duplicate object to have a different color. This would also help when you transform an array of object (via the modifier) into singular objects. They would all have different colors. Right now, they are all the same. And as it seems I would have to manually assign random color seed values to all of them, which in bigger scenes is a real problem. On top of that, every newly created object that the random color material is assigned to, has the same color. Again I would have to manually assign random seed values to object.
Maybe somebody can share some insight into this behaviour. And what would be a quick way to make the random color material work properly, no matter which object you assign to that matterial? For example 100 objects created by an array modifier.