Extended palette colour picker and save/load "favorites" for PTS watch-face customisation

Verification

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Extended palette colour picker and save/load "favorites" for PTS watch-face customisation

Description

I love that I can change the colours of the watchface elements in the PTS watchface, but I find the currently available palette very limiting. As of v.1.8.0 there are only 16 colours (and no orange).

Ultimately, it would be great if a user could do any of the following:

1. pick a colour by dragging a pointer around a continuous gradient palette, as per Photoshop and similar programs.
2. assign a colour by hex code
3. choose from a larger palette of fixed colours (a set of 32 colours would be desirable)
4. save and load particular "favorite" colour combinations

Considering option #3, a very nice 43 colour palette based on the official colours of Lego blocks, with hex codes, is available here, : https://lospec.com/palette-list/lego-brick-2016-palette

The issue names PTS watch-face customisation and the existing 16-colour palette, but no implementation files, tests, or entry points. Start by locating that palette and its colour-selection flow, then clarify which picker and favorites behavior are in scope. Done would require an agreed feature scope and corresponding verification for selecting and persisting colours.