I'm curious why you would do this. (Typically, the doors will match your windows.) One of the selling points for the doors is that they are 0 maintenance with the color goes through the entire depth of vinyl and never shows minor scratches. Once you paint them, you'll have to maintain the color for eternity.
You must also not have a homeowner's association that regulates this.
If you must paint them, you'll need to scuff the vinyl down really good and use a brush type paint. If you were to use spray paint, you'd have do so much masking that (IMO) it wouldn't be worth the time.