So for the DIY types reading this, here's a few tips based on over 40 years in the game.
1) "wet" the white areas in the clear with wax n grease remover. If they go away that's your issue, no color needed, if not it's definiately in the base as well.
2) when looking to blend new materials like nearly all clear coat systems, sanding out to really fine grit like in days past doesn't work. Best to go no more than 800. This will give the
new material a strong mechanical bond.
3) opaque reds are among the toughest to blend but there's some "cheats" one can do to lessen the angst. Dilute your color blend coat with clear base. Make it transparent so the
existing color shows through the repair area. This makes any mis-match disappear before the clear is applied.
4) the clear used for a blend has to be made up from whatever clear your using. This involves a lot of reduction (75-100%) and a patient steady hand. It wants to run really easy so
TAKE YOUR TIME. Also be sure to cover the entire sanded area but use less as you advance those coats.
5) when it's time to sand/polish you want to give it a 1st sanding and then walk away. This opens the top layers and allows for a full cure where hardness is the key to a successful
A good habit to be in is make test panels. Another good habit is to check color outdoors whenever possible. No matter how good the lighting is in the shop it never has the full spectrum of light provided by sunlight. You also want to check it in shadowed outdoor conditions. On metallics the "flop" is really important. Also, reducing metallics is tricky at best. too much will "wash" the poly (flake) and create silver specs that aren't in the existing color. PPG and other pro suppliers offer a product called "flop adjuster" for mixing. Good luck, and don't fear the blend. It can be a very rewarding experience as noted in the original poster's experience.