The main change that I’m aware of was the Merchant Shipping Act 1972 as amended. Where all collision regs were incorporated with agreed standardised data for lights , filaments, colours and sounds. Frequencies of whistles in proportion to size of vessel. All very technical but before implementation red, white and greens came in many questionable hues! The other thing was stopping peeps painting sidelight screens red and green and replacing with Matt black. This to sharpen up the cutoff angles of lights as red and green paint reflects the light outside required arcs. Similarly the filament in a navlight standardised as a single, vertical filament thus causing a point light source in the horizontal plane. As to river, canal and lake vessels, these are also covered but in general most small boats can pretty much manage with a decent torch. On the canals themselves in UK hireboats may not travel at night, private boats can and again only need to show a white light which is so they can see where they’re going. It’s rare to see boats moving on uk canals at night because you’re wasting valuable pub time! Incidentally, S L Canberra is post 1972.
Jerry.