Thanks Massimo.
Good point about the evenness of the line thickness. One might presume it was written in chalk, but I doubt that because had it been written in chalk then it would have washed off by the time of the crash probably (I am making presumptions here)? It was probably just done by an artist with a 'steady hand' using a paintbrush:)
Yes, I am beginning to feel that 'yellow' might not have been the most likely of the available possibilities, having heard the opinions of some people, and having seen your reply too.
About the inscription on the other side, yes, we know most of what was written on the other side because there is a photo of it, here:
The photo was found in this link
https://books.google.com.au/books/content?id=4fD7kCJimQ0C&pg=PA199&img=1&zoom=3&hl=en&sig=ACfU3U1BpuzDrZ-IZPZgFt8vUGG6UWd_nA&w=1280Here is how I have interpreted/hypothesised what is written on the port side (but the inscription is 'yellow' here still, I might need to change the colour of it)