My two cents.
A. Keep the palette monochromatic unless you want some other meaning than "Deep". You could use any color, but normally, a warm color will give you the additional meaning of "Hot", green of nature. Using blue could reference the sea, where darker blue means "deeper".
B. Keep the colors, either light enough or dark enough so you do not need to change the color of the text for contrast. But if you need the meaning "Deep" I would keep the dark palette.
C. Keep the colors saturated, especially on the inner circle, unless your concept of "Deep" also means "dark" or "murky"
D. Only use a multi-color palette if you add another meaning, like "urgency".
That is to answer the question, but you need to work a lot on the way you arrange the texts.
Not asked, but for the texts:
E. Try using a condensed font, this way you can make it bigger, in a more compact block of text.
F. Use bold text if you are using a dark background.
G. If you can reduce the space between letters, the kerning.
H. You have longer words than others, so try to maximize the size of the text using different zones of the circle.
I. You could try using another shape than the circle.
J. You could also rotate the text, but it can complicate the reading if you are not careful.
K. Ideally, you integrate the text on the circle, not "just put the text there" but this depends on the software you are using and the time and expertise you have with it.
The overall idea is to maximize the size and readability of the texts. Probably the users are struggling more about this rather than the palette itself.
Also, each shape means something. As you have the subsection in magenta, it looks that you are zooming in the center part (L).
See if you mean that or in reality, it is just a percentage of the outer circle, so you need to use the center of the circle for the lines to converge. (M)