I am getting mine repainting right now. I haven't seen what it looks like. I hope the colors match.
Are you sure your current paint is original? For your test, did you spray the base coat, top coat and clear coat? Not having any one of those would affect the final look. Also, paint ages and oxidizes over time, just like everything. When looking at the back fender, can you tell a difference between the back half, which is open to the air and sun vs. the front half that is somewhat protected under the seat? maybe sit your test piece outside in the sun for a week or so and see if it darkens at all? Normally you think about the sun bleaching out color, but if the clear coat has yellowed just a little from the UV rays, then it could make the blue look darker with out it being noticeable that the clear coat has yellowed at all. also, it could just be a bad color match. not much you can do about that. If all other things are equal, then you might need to reach out to Color Rite (or wherever you got your paint) or a Kawasaki dealer. There may be an easy answer as to why it doesn't match, but more than likely there isn't one... other than matching 25 year old paint is hard.
'03 VN750 a little over 4300 miles
F&S Rear blinker relocation
F&S Luggage rack
F&S Extended backrest
F&S Engine guard
Plexifairing 3 windshield
KM style dash
LED everything + additional brake lights &
LED plate bolts