Hello Mees,
Unfortunately it is not possible to access rgb-image data on CORE2 - size of single frame will be greater than the memory available on board (which is 192KB). Assuming you have camera with resolution 640x480 and 8 bits per color channel, single frame is 921KB.
If you are interested in getting other data from ROS into CORE2 board, you can use example posted at other topic: https://community-mirror.husarion.com/t/data-fusion/312/10?u=lukasz.mitka
This method allows to access any kind of data, as long as it fits into RAM.
You only need to change message type and topic name.
Regards,
Łukasz