I suppose it depends on how badly the colour has changed, mainly sun-fade probably.

does the paint look faded at all? If it's been looked after & polished regularly before you got it, then it may be ok..but if you're unsure, do the test piece first & see how it looks. If the slam panel, or wing-top edges under the bonnet look the same as the wing, then the colour won't have changed that much.

Good luck on the polishing, it's nice weather for it.