To each his own....
I'm sure someone here has done that - I'm pretty sure of seen pictures of someone's car with painted interior parts. Personally...I'd be really hesitant to paint those plastic panels. I'd be nervous about getting good adhesion. Your odds of not having flaking, peeling, cracking paint not too far down the road are not real good. You're going to need to do SOMETHING to prep the surface, and because those panels always have some kind of texture to them, the amount of sanding, etc., that you can do without affecting the look, or doing it unevely from one to the next, is kind of critical. You're also going to have little room for error. Each coat fills in the texture a bit - if you have to remove some, you're going to leave some in the low spots and change the appearance of that panel. If I WERE going to do it...I'd be sure to use good paint designed to be mixed with a flex agent to help alleviate cracking and peeling. I wouldn't count on your average spray can stuff. I'd be inclined to try to find some other, more reversible, way to accent the interior. Of course, if you can find spare parts at a salvage yard for a reasonable price, you could try it on them, and if you like the results swap them in. Then you've still got the originals to go back to, or still in place if it all goes to hell. Have fun!