It is very easy to get a poor colour match like you have there and it isn't an uncommon thing. The more I look at the photo the more I think that it is the front section of the car is the colour which is out, I mean if you compare the door to the roof they are the same tone.
How easy would it be to sort this? I think you could improve it greatly fairly easily but it will take a lot of time and effort to get a 100% panel match. Personally this wouldn't put me off of the car (providing it is priced accordingly) as there are a lot of cars out there needing the front panels replaced, which in turn means they would need painting. The panels have been done here and its just the paint which needs sorting.
Personally I would take this as an opportunity to repaint the whole car.