If you have a lot of parts and want to convert it to a mesh for performance, you would group them, export as obj, and reimportant as a mesh right? How would you make it so that details like colors also stay?
Also, does anyone know the actual performance impact of using meshes instead of a large amount of parts?
To help correct some misconceptions, when people import a lot of parts from Studio into Blender, there’s the critical step of cleaning up the mesh’s redundancies first, and then reimporting it back into Studio. Studio really chews up anything from the importer, so you need to spend time doing the cleanup.
To answer your question about colours, the answer is: It won’t maintain colours by itself. Since meshes are single objects, without a texture or vertex shading, they will always be a uniform colour and material. In any situation where you see a mesh with multiple colours, it’s using vertex shading or a texture
As for your answer on the performance impact, it depends on a few factors that make the process either really helpful or very minimal. If, for example, you’re trying to simplify a single tree that’s made of 5000 Parts to be a few meshes, and you’re reusing this tree everywhere, then the benefit is high since you’re reusing the mesh a lot (called Instancing). If you’re doing this whole import/cleanup/reimport process for a mesh used once, it’s probably not going to be as beneficial, for performance optimization or your or development time.
But there’s still a lot of “it depends” in the paragraph above. So if you’re able to, share a picture of what you plan on converting and we can suggest where to go from there 
I was just speaking generally, this is all I needed. Thank you so much for the insight!