Yes you can spray paint it black, but it will go back to being sparkly when you wear through the paint
Best bet would be to use black dyed epoxy over it to make it a flat color, or take an angle grinder and sand through the epoxy and glass until you get to the surface of the CF (or at least through enough epoxy and glass that it’s flat) and lay new epoxy and frit down (or a thin layer of epoxy to level it, and grip tape)
I’d use an orbital sander to sand it down in the easiest way possible while also keeping the surface as level as possible before redoing the top. Probably want to use some form of respirator to protect your lungs. It may take longer than an angle grinder but at least your life and limbs won’t be at risk unless you intentionally try and injure yourself when using it
If you want an easy way to have level epoxy, use some tabletop/ counter top epoxy. Just make sure to put a tarp or garbage bags under everything since it will drip off a ton of extra.
A cheaper way to color epoxy is to just grind down charcoal from an art store. The cheap vine charcoal will work well enough. If you don’t add enough it can be transparent in some areas but that is true of any powder pigment that isn’t mixed in well enough. You can also just use india ink which should also be pretty cheap.
Personally, I’m adding both in since my container of charcoal powder also has aluminium dust in it from when I sanded down hangers for painting. It is just to add a tiny bit of sparkle and a little extra strength.