Enable specifying an alternate default color for icon

As a developer
I can see icons in their intended specific color
(such as the orange presentation file type icon)
so they convey appropriate meaning to my users.

Some icons with an alternate default color are:
- FileSpreadsheet
- FileDocument
- FilePart
- FilePDF
- FileAssembly
- FilePresenation

---

### Dev notes

Icon components override the fill colors set into the SVG text. Most examples take their color from theme data at runtime for example. How will we continue to enable a component to override color when appropriate?

One approach to consider: Programmatically strip out fill values from all icons intended to draw color from theme data by default. Leave in fill values for the colored file type icons. It's important to so so programmatically so we can get new icons or updates from designers and not have to edit them by hand (or forget to, creating bugs).

Start by locating the icon components and the SVG generation or processing path, then inspect the named file-type icons and how theme colors currently override fills. Done means alternate default colors remain visible for the listed icons while other icons continue to use theme data, with the behavior covered by the project's existing checks.

Written by the indexing model from the issue text.