Here comes a gas bag full of opinions and observations.
Computer matching witha spectrophotometer is about 75% accurate and is meant to give a "shadeable" or "blendable" color not a dead on match. Getting a 75 is a passing grade but certainly not an "A".
I have a spectrophotometer (they cost several thousand dollars)and as useful tool and they really impress customers and instill confidence but I think it's lame to use it that way.
Car paints are photochemically reactive, that is, they are effected by the sun and changes color depending on how it has been exposed to it. If your car has been in service for a while, different parts of the car may be slightly different shades from one and other. (the bottom of your fender may be a shade different then the top but so is the bottom of the door so you don't percieve it)
There's the word..."perception".
Color perception, as we all know, is effected by the spectrum of light present and is interpreted, by varying degrees, differenty from person to person.
I have seen cars that the owners say have never been refinished or, have been, and claimed that they were not blended and they were, though it was unknown to them.
They don't see it so they don't believe it and who can blame a person for being hesistant when they can not see something with their own eyes.
I think it is neccessary to blend most colors into the adjacent panels so there a tolerable transformation of old into new color area.
Painting your entire vehicle to replace a fender should not normally be needed if the overall condition of the paint is good.
MvM, I think it's sad if you are having a service provided by someone and have to challenge their ability or conduct just to hopefully get them to rise to the occasion. Hope things work out.
Codered, $250.00 to paint a fender is a fair price but I wouldn't paint a loose panel and let the customer install it unless it was for a very old lawnmower.
Doing your car right should not require a total refinish but bolting on your painted fender is not likely to look like it did before the damage occurred.
I personally think Formula Red and most 3 stage paints are no harder and are maybe easier to achieve good color match with them. You have more to work with so you can dial it in.
Gas bag signing off.