An example of a blue-shaded Aldis lamp being used can be found in the account of Sub-Lt. R. Q. Drayson, R.N.V.R. in MTB 236 sinking the German auxiliary cruiser Komet in October 1942 (for which he was awarded the DSO). Peter Scott detailed this in his book The Battle of the Narrow Seas - and I heard exactly the same account directly from Bob Drayson a good number of years ago.
Key to the story is that Drayson committed the cardinal sin of losing contact with the MTB ahead of him when he stopped based on a blue-shaded morse signal on an Aldis lamp. There were no radios in these boats at that stage, so it was either an Aldis lamp, or stop alongside and use shout.