Most vinyl windows are white, and the reason has largely to do with the way vinyl expands and contracts with changes in temperature. Light colours reduce heat build up in the window frames, eliminating the bowing, bending and cracking that might otherwise occur. Some manufacturers do offer vinyl windows with factory-applied dark brown paint, but I know from nasty personal experience that this paint can lead to overheating of the vinyl, with expansion and structural problems.
All this said, white vinyl windows don’t always look great against a dark building and I can understand your interest in changing them. Are you windows shaded, even partially? If so, then try some paint suitable for vinyl. You’ll need to renew the paint from time to time, but it should last longer than paint on wood. Krylon is one brand of spray paint that’s especially formulated for use on hard-to-paint surfaces like vinyl. I’ve used Krylon personally with good results. I’d certainly go with paint instead of aluminum cladding. It would be difficult to install well over vinyl.