Did you thin with the water or Windex? Windex is what a lot of people use to thin the craft paint type acrylic paints, like GW, Vallejo, Reaper, etc. I believe the ammonia is supposed to help adhere a little better. But water should work too.
And no the Windex doesn't affect the color of the paint at all. I've used a whole lot of Vallejo Game Color White Primer on my minis thinned with it and there's no blue tint at all.
By the way, if you're using the airbrush to do minis with I would highly recommend Model Master Acryl white or grey primer. I've changed over to that recently. Super smooth.