The most common reason why your foundation starts to look grey or ashy within some time of application is the wrong shade of your foundation.
The mistake while buying a foundation, many test the foundation on their hands or their wrists or anywhere on the face, this results in you end up buying a wrong shade for your face.
Here is how you can find the right shade of foundation
Always try the foundation on your jawline and choose the shade that blends in perfectly with your neck.
Make sure you are in the best lighting that's neither too white nor too yellow.
Never wear the wrong shade again.