The component geometry used to create blocks should be created with a layer of 0, and other properties (especially color) set to a BYBLOCK setting. That way it will take on the properties of the layer it’s inserted onto, or the specific properties you specify in the properties dialog.
Failure to do this can mean confusion. For example if you create your block geometry on layer BLOCKGEOM, then insert them on a layer like INSERTS, you will find that layer INSERTS cannot be purged, even though there are no visible objects (when the layer BLOCKGEOM is frozen). In this case the invisible insertion point prevents the layer purging.