With the Matrix visual. Applying setting in the Format panel - layout and style presets > Style is set to "None", then within the Values box selecting two of the same colors within the "Text Color" ...
Tested on Version: 2.134.7447.1 64-bit (October 2024). This has been existing for a long time, I thought that it seemed fixed from Aug build (unknown version), but it could have been other settings at play, so cannot be for certain and I'm unable to rollback to verify.
But issue as explained above and reproduced by yourself is the same, and has been around for a long time.
The only 'work around' is to add two different colours with an extreme minor change in HEX to give appearance of being same colour for end users, else it defaults to grey and not chose color value.