It is possible, however there are several critical points to consider:
The warranty can be voided in these circumstances. Please confirm this before proceeding with any work.
To avoid painting the Access points, an option is to mount the Access Points in the plenum to provide a concealed position. Mounting kits may be required to do this. This option can produce radio frequency behaviours, since refraction, scattering, absorption, diffraction and reflection can come into play if the Access Point antenna is not installed visually or in RF line of sight.
Painting APs or antennas must only be done using specific types of paint that will not affect RF propagation, non-metallic is recommended. Some paints include metal flakes or other materials that can affect RF characteristics.
When painting the NEMA enclosure your AP can produce additional heat inside of the enclosure, which can affect performance. Due to this, lighter colors are recommended.
Avoid painting the LEDs. This will help for when troubleshooting the Access Point is required.