Thanks for this. As I just mentioned on Discord, this approach works for level 2 as well, but not for level 1. To color level 1, you can use, for example:
.ls-block[level="1"] {
color: rgb(168, 2, 132);
}
EDIT: To get level 1 to also have the right color when zooming in on blocks, you can use this code: Style Changes when drilling down a block level (edited)