Subtitles using CLUT colors 1-4 instead of 13-16. How to fix?

[nhope]

I have a problem with DVD subtitle colours. To test and illustrate it I have authored a very simple 16:9 DVD with Sony DVD Architect 5.2. No menu, just a 1st-play video with one subtitle track (with 4:3 and 16:9 subtitle streams).

In DVD Architect, subtitles use colors 13-16 ("Color Set 4") by default. I have set those to shades of white/grey/black. The menu highlighting uses colors 1-4 ("Color Set 1"). I have set those to green with differing transparency.

I then did my usual patches with PcgEdit to fix a couple of issues causes by DVD Architect's bugginess. Unfortunately PcgEdit can't correct this issue whereby finite subtitles behave as infinite subtitles, and the manual DVDSubEdit fix is very laborious. So I created new subtitles and muxed them into the DVD using MastroSBT/PcgDemux/MuxMan/VobBlankers as per the guides here and here.

The resulting DVD is using colors #1 to #4 in the CLUT (the yellow ones) rather than colors #13 to #16 (the white/grey/black ones) as they should be. At least I assume that is what is happening.

I have tried to find a fix in PcgEdit but I don't know my way around the program well enough to locate the problem and assign the correct colours to the subtitles.

A backup of the IFOs from my reauthored DVD is here.

Does anyone have any suggestions on the cause or the fix for this problem?