The auto-generated text color is too light

Report from client:

Their design is using `#3E3D39` as heading color, when they put it in the "Text Color" in "UI Settings"
The auto-generated secondary text color in the AuthUI becomes too light.

They expect the description and the heading in AuthUI both be `#3E3D39`


No file, test, or entry point is named. Start by reproducing the color choice in AuthUI after setting #3E3D39 in UI Settings, then trace where the secondary text color is generated. Done means the description and heading both render as #3E3D39 for this setting, with coverage for the reported case.

Written by the indexing model from the issue text.