Step 3 - Now add lights

Then I labelled another column for "Lights".

I used R for Red, W for White, and G for Green, if they were all-round lights. I used M for Masthead and S for Sternlight. For the extra stern light for vessels engaged in towing I used Y for Yellow. 

For vessels engaged in fishing I put down both G over W and R over W. Now I just have to remember which is for which: trawling or other. 

For larger power vessels, I used M + M to indicate one masthead light forward and another aft. You might want to put something like a bar above the second masthead light to indicate it should be higher than the one forward. (Do you want to write "50m" to remind yourself of the cutoff for two masthead lights - one in the fore part and the other abaft and higher?)

For the masthead lights for towing, I put one M above another or three M's vertically. Then a stroke and the Y over S for the stern lights that indicate towing. (Should I have included 200m for the cutoff between 2 and 3 masthead lights?) And, I'll just have to remember the lights that are used on the tow (barge, log boom, etc.).