The way I have our blocks setup (architectural electrical) is each block is constructed on layer 0 as it should appear in a 1 = 1 drawing. The color and the linetype are both set to BYBLOCK.
Then when a user inserts a block (via a toolbar button) it is inserted on the current layer and scaled up by the value of LTSCALE.
If the user changes the layer, the block changes in color and linetype, to the settings of that layer.
As an example; the same block is used to show a standard 2 x 4 fluorescent fixture that is new (CONTINUOUS linetype, blue) and one that is existing (DASHED2 linetype, green) simply by changing the layer it is on. This makes it simple when, for instance, an engineer asks to get a print of new fixtures only. Simply freezing the EX-LIGHT layer hides all of the existing fixtures.
In the past, the way people at my company did things, they would explode the block and change the color and the linetype of the various objects. You can imagine what a mess that would cause.