Greencode, maybe a silly question, but have you actually tried the paint on your car in the stonechip to see what it looks like? An area of paint applied to what looks like a white plastic lid in your photo isn't necessarily the best test. If you'd applied it to a black lid, it would've looked much 'whiter'.
With the Chipex kit, if the colour match isn't good on the car, the paint you've applied can be gently removed with the blending solution.