If you have more than one MyStrom bulbs you can combine them together in a group. So you can control them all together. You register such a group as device.
You have to give an unique ID to the group, then you add all bulbs you want to have in this group. A MyStrom bulb can be registered in more than one group.
You can control a group like a bulb with a color action or directly in userinterface control.