Colour change your lookin at about 2k + mate, trust me ive done it its a fookin bitch to do!!! whole car has to be stripped prepped, painted then put back together.
Same colour again if done fully will still need stripping so anything from 1k-£1500 is fair really.
If they do a blowover some places start at £800 + as they just do it without painting the shuts etc so leave the doors on etc.
You get what u pay for at the end of the day mate!!