Paint on cooling fins has been discussed here before so I am not going to express yet another opinion nor hijack this thread, but if you have trouble getting to sleep and really want to know you can read this
https://nvlpubs.nist.gov/nistpubs/nb...cpaperT254.pdf or you can google the subject to find thousands of links that will tell you the same thing and come to your own conclusion.
If you are already fast asleep here is what the research conclusion is
"The experiment with the Melloni cube has, therefore, two
important applications, depending whether it is desired to (1)
decrease or (2) increase the process of heat radiation; and it may-
be enunciated, as a general principle, that clean, bright surfaces
of all metals or paints of metal flakes decrease the intensity of
thermal radiation (are poor radiators; that is, have a low emis-
sivity), while the nonmetals, or paints of nonmetals (oxides,
oxidized metal surfaces, etc.) facilitate or increase the rate of
heat radiation."
As a moron in a big white house says "Follow the Science" and don't believe the rumor mongers!