We are sorry to hear about your experience with the recent updates on your Samsung Galaxy phone having issues with the color palette not showing on volume bars, and we apologize for the inconvenience it caused you.
It's a good thing that you were able to spot the difference, trying it out after an update, but it doesn't meet your expectations that it should be better than the latter, so I will feel the same.
If that doesn't fix and at the same time, find out the exact root cause of the problem, you may submit an error report through the Samsung Members app as follows:
Step 1. Long press Samsung Members icon on Apps screen and tap Error reports.
Step 2. Tap OK on agreement popup to send system log data.
Step 3. Select Symptom category "Settings/System".
Step 4. Describe the problem in details and SEND.
How to submit an error report on Samsung Members app? | Samsung PH
For more assistance and guidance, you may contact us via our online Samsung Customer Care support channels below.
Have you tried editing and applying the colour palette through theme park?
Or just changing the theme in sound assistant?