Yes it's the best way.
With the 255 IMC colors it is hard to create a longer color palette with logical color sequence. I self use color palettes with up to 30 color but my favorites are 21 and 24 colors.
It is sure possible to include 40 colors, but there is a border with visible differences, but even then if we have AT5 v13 (any hexadecimal colors), the color differences make it necessary to summarize depth areas for deeper waters.
e. g. this any sample with 19 colors for 40 m depth
1
2
3
4
5
6
7
8
9
10
11, 12
13, 14
15, 16
17, 18
19, 20
21-25
26-30
31-35
36-40
Each user can adapt such sample for his purpose. But for open sea (norway etc.), i recommend/use the scheme from Trevor for better overviev.
Best wishes
fjordfisher
P. S. Sample schemes HDS only!