David,
There is much discussion reagarding a term known as "conspicuity" or if you prefer, "visibility".
Manufacturers build machines to meet DOT requirements. These are fairly straightforward.. Cottage industries spring up fulfilling the "individual" desires for modification. Major manufacturers are also somewhat involved... There are as many ideas of what "works" as there are people.
Studies (i.e.; Hurt Study (I think)) have shown, by creating a "triangle" of lights in the front makes our machines stand out, to be "conspicuous". BMW's done that, somewhat beginning with the 05 K1200LT.
Adding "MotoLights" mounted down on the calipers expands the size of the "triangle of light". Also, adding the PIAA lights under the cowl adds to your visibility by increasing the "triangle".. as well as being able to see!
Light colored clothing is best.. unless you live where it snows all the time!
With the reduced cost, low power consumption, low heat, functionality in hostile environment and choice of colors, LED's are becoming popular. The "limitations" being angle of and output (lumens/candlepower).
Another option is "reflective" products. These, too, are numerous and of personal choice in their application and use.
We've all heard "loud pipes save lives"... but they are very annoying.
So much of this is a matter of personal choice. Of course, that's the first thing you must overcome to ride in the first place. What "works" on the vehicle... what makes someone comfortable they've done all they can to be "visible", can be any number and combination of lights, colors and application of technology.
The best thing tomake you conspicuous is your brain.