I'm working on a program to solve a single face on a Rubik's cube. In trying to find a way to reach the optimal number of moves I found God's number (the minimum number of moves needed to solve the cube in any state). My question is what is the God's number for recreating an arbitrary 3x3 pattern of colours on one face of the cube is. To be clear, this means that the cube will have to start off in the solved state and end up in a state where one of the 6 sides perfectly matches a pre-determined 3x3 grid of colours.
I haven't been able to find it anywhere on the web at the moment. I thought to follow the steps used to find God's number for the whole cube to work it out, but I have no idea where to start.
[EDIT]
I wasn't very clear with my question. I've now clarified it. Thanks to @hamza-abbas-zaidi for help writing.