See, the light being the problem doesn't quite add up. A shop light usually washes out color and makes it harder to see, it doesn't invent a blend line that isn't there. If you were chasing it for 6 hours on a silver Camry, that paint probably has a tri coat or a heavy metallic that flops hard under different angles, and you were reading that shift as a blend edge. What bulb is in that light and how far off the panel are you holding it?