1. The CRL states for basic approval, the recessed pill shape can be matte or metallic black.
2. Do you know what material it is printed out of? I used a medium viscosity CA glue for my 3d printed helmet and it bonds pretty quickly, even faster if you buy a kicker spray for it. Only thing is, if you use that, it will not be removable like E6000.
3. Are the metal ones from PhoenixProps? If so, I have the same kind just painted them according to the CRL. Without knowing how they were glued on, there is real risk of damage. E6000 is usually forgiving when it comes to removing parts. CA glue...not so much.