I am not sure when you introduced the background colour in list headings, but it surely looks odd - in the sense of not properly aligned. The heading text should probably be in the middle between top and bottom of the background colour.
I saw in older screenshots that there was no background colour in previous versions and that worked quite well I think. But if you want to retain the background colour, the alignment should be fixed.
I am on 1.11.0B1, but I noticed this in a previous version already.
I did not add it and it’s only visible in the black theme, will see what Google change and try to fix
Edit: So actually I can’t fix it’s reported and Google will provide the fix at some point. I’ve ensure some consistency in next release so that it’s less ugly but only Google fix will return the bar transparent.
OK, the heading is now fixed, but with it all “cards” e. g. on the home screen, but also in grid view lists lost their background. It is still usable, so let’s hope for the Google fix and then maybe restore those?