During my project for my photography course I have to photograph on location and edit the best photos with the model, on my MacBook. At home on my MacBook I export the newly created collection to a catalog (including the negative files), copy the directory with the catalog an all other files via the network, and import the catalog in my standard catalog on my iMac. On my iMac all the color labels of the imported photos are gone in my standard catalog, and,very strange, the color labels are also gone when I open the exported (and copied) catalog on my iMac. Do I miss something?
I don't think this is anything to do with copying via a network.
My guess is that you need to look at Metadata > Color Label Set. Try comparing the settings on the two computers. If they are different, one computer may not know what the other means by red, yellow etc.