Plant food will help with the number of blooms it produces. And if it has micronutrients nthe intensity or richness of the hues. But for hydrangeas the actual colour they turn besides genetics is dependent on soil ph.

All that matters though is that your hydrangeas look pretty and youre happy with them.

I know a guy from the uk that for some reason hates hydrangeas. I cant think of why. But his wife loves them and to spite him plants them everywhere. He often writes to me to complain that theyre taking over his yard.