I used a grey base ...i think it was PPG.....i was told you should not excede 17% of color to the primer but we kept adding green until we got the LIGHT MINT color I was looking for....funny thing is....it didnt start really working until we started adding the darker greens...like a hunter green....so to tint yours blue...I would suggest a dark color blue to mix in the grey...here is a pic of my 96 Ranger with 03 front clip primered mint green