In the default mode, when you set a shared group as the current group (see Set Current Group) and create some entities inside the group, the color used to draw the entities is the current color (see Color). If you change the current color and then end the editing session on the group, next time you edit it again you will find that the color you set last time you edited the group is still current inside it.
You can change the default color mode, choosing to always have the same default color when starting an editing session on any shared group.