Not dreaming at all, it paints very well with conventional gloss paint as the paint solvent glues the paint to the PVC.
At least for gutters and downpipes; I wouldn't try painting PVC windows although there are special paints for doing this (and specialist renovation companies who will come and do the whole job in situ - it's quite popular for renovating conservatories)
Never painted a window, but as they are toast, what have you to lose.
Gutters & pipes painted and lasted 30 years untouched.
Clean and degrease. If yoo live near a road or under a flight path you may be surprised at the filth.
Rub down vigorously with 100 grade paper. The plastic surface must be cut. Get into the corners and edges.
Degrease with white spirit. Use a stiff brush to get into the corners.
Paint with solvent paint, top coat only. No primer nor undercoat. Two coats. For a better finish rub down with 400 paper between coats.
You can paint the frames one colour and the sashes another.
A good chance perhaps to decide what colour(s) you want on the finished house.
Let your imagination go.........
(But no dark colours on the south or west, because unless you have trees to provide blessed shade, the sun will destroy it)
Ivor
Bi-colour windows Sikkens AZ, plastic gutter Dulux gloss, iron stackpipe & small conservatory Magnet lead paint, woodwork creosote & tar.