the 194's have a bulb holder that spins into the back of the cluster.
YOU CAN NOT CHANGE THE COLOR OF THE CLUSTER BY CHANGING BULBS. YOU MUST REMOVE THE GREEN PAINT OFF THE BACK OF THE CLUSTER FIRST.
if you remove the green and add blue leds you will get this(not the only method)
this isnt for the weak you must remove the needles which potentially will turn your cluster into junk if you dont put them on in the same place.
N3elz has a how to for the switches which is very good.