Many people mix black and white paint when they are trying to create gray, but the highest-quality gray shade is made by mixing in blue and orange. This may sound strange, but the final result is a much brighter, cleaner gray than the muddy result of using just black and white. If you have accidentally used too much blue while mixing your paint, you can fix it easily by adding colors that will lighten it and create the gray shade you are looking for.
Add equal parts of orange and white to the too-blue gray paint. Only add a small amount at a time to make sure you don't completely cancel out the blue.
Blend the colors thoroughly, using a flat-headed paintbrush to ensure that none of the white or orange paint hides within the bristles.
Add more of either color to help achieve the desired effect; orange paint will make the gray appear brighter, while the white will lighten the shade to your liking.