If I want to permantly change the color of my car, what is a good method?

There is MUCH more involved. For a very good paint job the car, the current paint has to be stripped off and the body sanded down to be smooth.In many spots car parts will overlap and the old color paint will be in the areas you can't get to, unless you take them apart, so insides of hinges etc. can be a problem and the doors hoods, trunk lid etc should be removed and sanded down as well and painted then put back on. Once the sanding is done and the surface is smooth, then the undercoat must be applied evenly, a few coats. And once all that dries, it must be sanded and smoothed as well before the actual paint goes on.

Of course if you just want a paint job and don't really care how good it looks, a spray can can suffice.

If you want to use spray cans on your car - go right ahead - but you won't be happy with the results and will appreciably lower the value of your car.

I'm saying that Yes, it's a little more than that: that's why a cheap paint job costs $1000.......a good one $4000.......so if your paint is good and you just don't like the color - - a lot better to accept it the way it is, or trade for another car.

Better to ask a professional than to ask random people on the internet