Added an OLED theme, picked it on my phone, and most of the screen was still grey. Rather than argue with my own eyes I took a screenshot and read the actual pixel values out of it, which took about a minute and saved me a lot of guessing. The background was 121212 when I had asked for pure black.

Turned out the theme was never reaching the screen. The app builds its colour scheme without setting a surface colour, so every page fell back to Material’s own default grey and quietly ignored the palette it had been handed. One line, and the background went to 000000 and the cards to 080808.

The bit I liked was the leftovers. A few tiles stayed light and I was about to go and edit the seventy something places that paint card backgrounds by hand, until I noticed the colour was 3B4548. That is not grey. Grey has equal channels. It was the teal accent bleeding in, because Material tints raised surfaces with your primary colour, so that was one setting too rather than an afternoon of find and replace.

Also checked the contrast while I was in there and every accent clears AA on black between 9.37 and 18.80 to one, and found that choosing OLED did not survive the phone flipping to light mode and back, because the theme listener was overwriting whatever you picked. Not finished yet, the tile fix still needs a look on a real device.