The color marks are stored in the catalog.
How are your transferring the catalog from one computer to the other?
Just some hints.
a. Lightroom by default stores all the work you do in the Catalog File, if you choose to store the info into a .xmp sidecar file /or into the file header of a jpeg, tiff file its possible however not all of the info is stored in the .xmp / file header.
b. For you to see the same info / edits on your iMac at home and your MacBook on location you need to use the same Catalog or a Copy of the Catalog.
c. Lightroom does not sync info from your Desktop to your Laptop Computer. Sync is only available from a computer to a mobile device e.g iPad, iPhone, Smartphone
the catalog sits on the MacBook which I connect as an external harddrive to my iMac. The Lightroom app takes the catalog from there. That is why I am puzzled about not seeing these color marks, but all the other adjustments.
I run upon a minor but strange problem: I work with my Lightroom catalogue on two different Macs (iMac at home, MacBook on location). When I mark a photo, say on location with say the color green for "accepted", I would expect that I can see this green mark at home, when I open this catalogue at home. Alas this is not the case, so I have to mark the accepted photos with some stars or a keyword to have the results when I work at home.
Why is this? I would expect Lightroom to store all adjustments, remarks and such applied to a photo in a way that they are still here when you open this catalogue again, even on a different Mac. Any ideas or even a workaround (except setting stars or keywords)?
Your problem is probably because the two computers have different Color Label Sets enabled. See Metadata > Color Label Set. To fix it, you need to enable the same Color Label Set on each computer.
Lr doesn't actually store the colour label as a colour. Instead it records a text value, and then uses the Color Label Set to figure out that the text value "accepted" should be shown as a green label. So if another computer has a different Color Label Set active, Lr will think that you want green to be shown for images with the text value "green" in the colour label field. Hope that's clear.
@john: thx a lot, you solved my problem!