The bug

If a new trim type is added via a data pack and resource pack, the item forms of trimmed armor pieces behave unexpectedly.

How to reproduce

1. Download the resource pack and data pack attached to this ticket
2. Apply the resource pack
3. Create a new world with both the experimental 1.20 data pack and attached data pack
4. Obtain a smithing table, trim smithing template, valid material e.g. an emerald and valid armor piece
5. Note how the output armor piece looks

Expected results

The item and 3D rendered forms of the armor piece should have the same color as each other, which is also that of the trim.

Actual results

The 3D rendered armor piece appears correct, however the item uses the glowstone trim color.

Further notes

The resource pack and data pack have glowstone's item_model_index defined as 0.05. I previously had this set to 1.1 instead, and this had the effect of making the glowstone trim that the data pack adds look like amethyst on the item. I didn't test any other materials other than amethyst and glowstone at this time.

Side note: having a glowstone trim in vanilla would be interesting since that'd bring it more in line with its cousin redstone, however that's ultimately a feature request.