What do the colors in the outliner indicate?

What do the colors next to an object indicate? What does it mean if they are the same color? What if one is missing a color? Or, they are different colors. See the attached example. What are most of these plants purple and one is not?

Thanks so much.

Hello ,

Thank you for posting in the community and the colors on the side means that one element is an instance when they have the same color. So the one that does not have a purple color means it's a unique mesh and changing it won't affect the other ones that are instances.

Kind regards,

Vincent B.

If I want them all to be instances with each other what is the best way to do that? I tried replacing them all and it doesn't seem to do it?

Follow up to this, how much does instances vs copies impact performance. I have a lot of plants in the model and really they could all be instances of eachother if they are the same species but many are copies. Should I update them to make them instances? How would you recommend doing this? Even when I replace them all they remain copies and not instances?