OP wrote: "I have a lot bad experience dealing with car repair peoples"
Maybe it's because of situations like this. Why don't you just have him paint the whole car right now? (the same color - see below) It won't cost that much more - unless there is more body work involved.
In all fairness, you're asking them to do half the repair. Personally, I'd pass on your job. Over the years, I've seen guys who were trying to cut corners show up a year later. They waited too long to get paint down, and now they have a corrosion, rust, or surface problem that needs repair. They typically want me to repair it again, for free. I would tell them the same thing I'll tell you: Bodywork with no primer, paint, and clear coat is just asking for trouble. I'd urge you to do the repair correctly the first time.
Edit: Painting a car a different color is a huge expense to do it right, and could be a real waste of money.