Four of my Alfas (33,33ti
,75,146) have been in Rosso. Not one of them had LESS than 3 shades of colour
Paint fades after time [fact] esp red but when the paint is mixed the colour code off the panel tells what colour it was when it rolled out of the factory [also fact], the paint shop then have a series of colours that are slightly faded from new on wee colour cards and this is held up against your bodywork to see how much fade there is [spot on]. The paint is mixed to match this colour EXACTLY. [Exactly Right]
(My remarks in square brackets)
See, Decky knows the score exactly! I was never a sprayer but I have worked in a paintshop who had thier own mixing machine (rare in 1985!) and this is exactly how it was done and still is.
The colour swatches (wee colour cards) each have a formula for the mix on the back and that gives the final result when the paint is dry!
You cannot do it "by eye" as AlfaLincs suggests as the paint drys to a different colour to its liquid state. (Perhaps he meant that the swatches are matched by eye.)
The formula is for a given quantity of paint, say a quarter litre, and would read something like:
RED 5514 - 90Gm
RED 5254 - 30Gm
YELLOW 8789 - 15Gm
WHITE 2476 - 7Gm
Now the actual numbers above are totally ficticious but give you an idea of how it works. The four figure number is the paint reference of the paint company that supplied the mix machine. I assume there is an industry standard for that.
So Picard there is your answer. Get them to respray the bumper in the proper colour.
Or if they are not capable of such a complicated task because they buy their spray cans from Halfrauds,
get them to send it to someone who can, or pay for you to take it somewhere