What you can do is where the red meets the old and has a straight line is to sand this back very gently with some fine sandpaper... dont d it wet unless you can guarantee that you can keep it 100% contained. Reason is that the run off will leach into any open timber and then you have the task of pulling it out of the wood as it will tint it.
If you lightly sand that line, it takes the new paint back slightly and will "feather" the two paints together.
You can lessen this task by pulling up on the brush and create a greater distance between rush and PF as you near this line.. means you have a thinner paint here and so a lesser line.
The blue/green will match better when protective coat is down.. chances are on this that it has turned greenish over time as the linseed yellows..wouldnt surprise me if you didnt have a good match for the factory colour
