I took the original skin made by Korbo and modified the colour of the jumper so it matches the new Netherite armour with the Diamond Armour Trim. The new colour is the kind of dark blue-ish purple-ish colour, with a teal-coloured J emblem at the back, resembling Diamond's colour on the armour trim.

I used Blockbench for reference, where I edited the jumper's colour, I then finished it up in GIMP, where I applied the original jumper's texture by removing all but the jumper (I also removed the J from it, leaving transparent pixels) from the original texture, and then applying Divide blending mode on the original texture, which brought the texture to the new colour.

This new colour then should match your Netherite Armour with the Diamond Armour Trim.