Go Minimally Green

Starting with a $5\times5$ grid of yellow squares,, you can pick the squares one by one and turn them green, provided that the square changing color shares either $1$ or $3$ of its edges with the yellow squares around it.

What is the smallest number of squares you need to turn green before all the remaining yellow squares fail to satisfy the condition, so that no additional squares may be turned?

Inspiration: weekly problems