OK, to be sure: the snippet is for preview mode, not edit mode! Does it adapt the styles in preview mode?
Edit: This code should work for edit mode (at least it does for me):
.cm-s-obsidian .HyperMD-list-line-1 {
color: red;
font-size: 1.2em;
}
.cm-s-obsidian .HyperMD-list-line-2 {
color: yellow;
font-size: 1.2em;
}
span.cm-formatting.cm-formatting-list.cm-formatting-list-ul.cm-list-1 {
color: red;
}
span.cm-formatting.cm-formatting-list.cm-formatting-list-ul.cm-list-2 {
color: yellow;
}