Steve,
Ok I think it's time for me to get some sleep! Sorry about the tile colour confusion. I got the colours right but in reverse - as you said. I was working from memory. Also that seam that you have running through all the tiles would not have been there. The outer tiles (nearer to the paneling) only had half a tile running on either side (and thus half an octagon) and I guess when the tiles were sold in 1935, they were layed over a full floor and the tiles were joined to cover a large area, rather than the 5ft 4in corridors they originally covered. The tiles themselves were 12in wide with an octagon in the middle and no seam.
The 1st class corridor paneling was like the Gym's, now that you pointed it out, only all white, and without the fancy scroll capital on the columns. Also, those cornices shown in the auction lots with the brass/gilt swags were the cornices from these corridors. They were all white with the swags gilt. I don't know how much artistic lisence you should apply to your models, considering you're representing something that has never been seen before. But it is your work after all, and you're doing a good job of it. The corridor lamps were the 7.5in cut crystal lamps also seen among the auction lots.
White was used extensively throughout the ships and it might seem boring, but it was the best way to provide the optimum lightness especially in interior sections where natural light was not readily accessible - such as in the two main B and C deck corridors.
Regards,
Daniel.
The octagonal and diamond shapes were an aqua green, while the main area of the tile was more blue, there was a slight distinction between the two colours which is not readily evident in the render. However as you said it is only a rough render. Also along the perimeter of the paneling was a border, much like the border in the grand staircase (but it was the aqua green colour).