If two stage paint was originally used, then touch up will be of a different composition, as opposed to a single stage base. Solvent versus water based color coats is another issue these days since once these undercoats dry or cure, then the next coat may not melt into it creating an adhesion issue. May or may not match even if the same color recipe due to chemistry, ability to blend wet into dry and other appearance factors, not just pigment. Then there's the issue of clear coat if one was used originally. All that said, any auto body supply can cross the paint codes into PPG, Dupont etc. and also give you advice on best way to proceed with their products or even a good touch up shop that knows how to blend.
Experience is what you get when you don't get what you want.
"We'll be friends until we're old and senile,....then we'll be new friends."