I was thinking A4 B7 with the 3.2 FSI, but there's only one red one on ebay and its an auto
https://www.ebay.co.uk/itm/2006-56-A...5/173354093760
There's a bit more choice if you go diesel
https://www.ebay.co.uk/itm/2005-55-A...R/163070549505
This red-painted 'Black Edition' (ie de-chromed) looks lush, but misses the drivetrain mark completely with a 2.0TDI auto
https://www.ebay.co.uk/itm/Audi-A4-2...d/142816407842
Going up a size to the C6 A6, there is a darker metallic red available but its pretty rare. Otherwise everything is monochrome or dark blue. Not much choice of fun colours there, and most of them are diesels.
You might have specified a unicorn there
Maybe buy something monochrome and wrap it a fun colour?