Hello All,
Sorry for the confusing title, but I have no idea how to write it down

.
Imagine that I have a numbered list
- A
- B
- C
In the beginning I want A in bold ( or more visible) and B and C faint or in light grey.
When I select B, I want that A goes faint as C.
When I select C, both A and B are faint.
I could play with animations, but is a bit long.
I attach a img to give an idea. It is only one text box, and not 3
Thank you.