You are correct about that: Wisconsin Statute 347.07 "Special restrictions on lamps and the use thereof."
... (2) Except as otherwise expressly authorized or required by this chapter, no person shall operate any vehicle or equipment on a highway which has displayed thereon:
(a) Any color of light other than white or amber visible from directly in front; or
(b) Any color of light other than red on the rear; or
(c) Any flashing light.

and statutes here do specify that modulating headlights are allowed on motorcycles during daylight.
But the set-up I'm thinking about can also do a steady glow; that would be legal and might be helpful on an overcast day.