Disabled button text color appears green by default

[LuminaSapphira]

Describe the bug
The text color of disabled widgets is green when the regular color is not.

To Reproduce
Steps to reproduce the behavior:
The issue can be seen in the demo at https://www.egui.rs/#demo. Just uncheck "Interactive" in the widget gallery.

Alternatively,

1. Create a disabled button with text supplied as &str (or RichText with no color supplied)
2. It is green.

Expected behavior
The text is a faded out color of the normal text color.

Screenshots
Enabled

Disabled

Additional context
As of #3727 (tested by rolling back to git rev e36b981), the button text appears green. It seems like it is not replacing the new PLACEHOLDER color with the appropriate color when disabled (it is graying out the PLACEHOLDER rather than the intended default color). Using RichText with a color does not display this issue.

[YgorSouza]

The text also turns white in the light theme

[emilk]

Thanks for the report!