>Any reason the plot coordinates are transposed vs the other plot? I'd intuitively always expect depth to be the y coordinate.

It is temperature vs. salinity, no depth coordinate.

>Is there any value in providing some colour to the graph? Potentially using the height values?

It could be coloured by depth, I chose not to as it is not common practice to do so. Different colours on t-s plots are often used to distinguish between different regions or measurement campaigns. For this plot I used multiple locations just to get a nice average picture, so I'm not sure if it is worth colouring by latitude or similar.