where did you get the spray you used? was it main dealer cans? iirc Mercedes were about £9 for a 200ml can but the colour matched perfectly on my silver car and the can nozzles were decent quality giving an even fine spray. I did my back bumper and its as good as it was before with no difference in shading. much time was spent on prepping though and I think using the wrong colour of primer can alter the finish shade a little.