Inspired by this question, I actually rather thought of the opposite - to make ignored questions even more transparent. Currently, they are visible enough so it becomes a bit difficult to distinguish between ignored and not-ignored ones. At least for me.
My personal workaround was to check "Hide ignored tags", but that leads to weird "bugs" (undesirable behavior that is, I was told, by design).
I'm not sure how this issue should be solved. Apparently opinions differentiate quite a lot here, and customization like a slider controlling transparency are definitely overkill (and maybe not even possible to implement).