Disabled button is transparent on a floating background

**Describe the bug**

Currently, the color used to represent a disabled button in vanilla is a lighter (more transparent) hue of the original button color, this works well for the most part, but is problematic when the button is made to float over a dynamic background (e.g: a map)

**To Reproduce**

Steps to reproduce the behavior:

1. Create a button that floats on a dynamic (multi-colored) background
2. Make the button disabled

**Expected behavior**

The button should be opaque to improve readability

**Screenshots**


The issue names no file, test, or entry point. Start by reproducing the disabled button over a dynamic background and locating the vanilla button styles; done means the disabled button is opaque and remains readable in that scenario, with relevant styling coverage if available.

Written by the indexing model from the issue text.