This is a moot point for any Trek culture that has FTL propulsion and sensors at their disposal.
That's quite a stretch based upon something that doesn't exist in reality and thus is ENTIRELY defined by storytelling requirements.
The material of the hull might provide an effective measure of reflecting/refracting sensor scans but not the paint itself unless of course they create a paint with reflective properties, but it would be much easier for the hull material to be sensor proof (which is often associated with highly advanced cultures ... our heroes would have to use a dampening field around the hull) instead of using tons of paint.
Ummm... why would it be "easier" to do that than to use the MOST MECHANICALLY ADVANTAGEOUS material for the hull structure and then just apply the sensor dampening material, which is probably not as mechanically robust (I could go into another lecture about why certain materials are better than others again, but I'd rather not) in a thin layer over the top.
"Using tons of paint" over two trillion tons of metal is still superior to using tens of trillions of tons of less robust material in the construction of the vessel to achieve the same mechanical strength.