As someone who frequently turns plugins on and off, especially when comparing them, I completely agree the distinction between on and off (bypassed) when viewing in the effects bin should be more distinct. The mouse hover behavior even says bypass this effect when the effect is already bypassed. Since touchscreen use is also an option for some, I'd have to push for the easier to identify color difference.
It's a problem, easily reproducible, and a more distinct "off or bypassed" color identifiable by a quick glance would help Sonar maintain it's reputation for the easy to use Skylite GUI. If the mouse hover said enable when the effect is bypassed that would also help. Wouldn't this be the "low hanging fruit" of problems to solve ?