Primer question

I have a kit I’m working on, and its molded in white. The end paint job will also be white.

Now I’m going to start putty and sanding soon and then I would prime.

I have grey primer, so am I going to have issues spraying the grey primer then trying to repaint white?

it kinda goes against the principle to spray the lightest colour first, then paint darker and darker…

I have used gray primer for years and never had a problem painting white over it. It may take an extra coat or two depending on how gray your primer is. If you really want to scrimp on the white paint, there are white primers available.