SD86
Banned
Light blue is a mistake in the translucent Z/Champion types of plastic. I had a Champion Valkyrie in this color and when playing courses that get more rain or have non straw grass I found it hard to find the disc in green grass. That Dayglo yellow/green is one of the best in translucent plastic outside the non swirly/marbled pink discs.
It depends on just how light and how blue the disc is. I have some blue Champion discs that stand out very well and are easy to spot, and some that (like you said) don't grab the eye as well. And clear blue Champion discs can be difficult to spot in water, even shallow water.
Bright pink Champion discs work best for me, though any very bright color (except maybe purple) does okay.
Red can work if you have the bright reds that are more to the raspberry/almost pink side and not the dark reds and basic reds that are more commonly found. Dark red is a really bad choice as the disc can look like some types of dirt/mud.
In Champion, a bright red can be okay. In opaque discs, even light reds that aren't outright pink can be difficult to see. And as you said, a dark red disc can be a disaster. I have a dark red Echostar Tern that flew great but I had to stop using it: I found it a couple of times by literally stepping on it before I ever saw it.