They do pop out. Be aware though. Prise the 'chrome' surrounds out, and the wire mesh is free to be removed, or more probably fall inside down inside the wing. Fortunately I had a snakey grabber and an hour to feel grab and remove.
ahh ok i was thinking of just spraying the inner mesh while i did the front vents tbh. might just mask up with them in seem a ball ache. inside the wing is black anyways i guessI had similar thoughts around painting the vents black on my car so bought a spare from Eurospares to trial paint. I found the paint I used didn't adhere very well so make sure you rub them down well and use primer... The vents do just push out although have a catch section at one end, here are some photos: