You can tie the fly without the bead, then put the bead of your choice on the line itself just before tying on the fly. That lets you change the color, weight, size, etc of the bead without having to have umpty-seven different flies on hand.

I didn't come up with that approach but I have used it successfully. I've even used it to help a beadhead fly get down faster by putting a bigger bead on the tippet before tying on the beadhead fly...the bluegill didn't seem to mind at all.