I recently upgraded from the Pixel 6 to the 9 Pro and I notice that there is extremely poor contrast on the popup menu for words that underlined with the red line letting me know it isn't in the dictionary. It is nearly impossible to see the words in the list without really looking closely.
See for yourself: https://i.imgur.com/23NCSmc.png
If the font color was white instead of black, this would fix the issue.
This was never an issue for me on the Pixel 6 and changing contrast in display settings makes no difference whatsoever. I've also tried 3 different keyboards but it isn't a keyboard issue.