Why are mexicans so dark if they supposedly descend from Spaniards, I visited Spain and they're white?!?

Mexico as a whole is very racially diverse & Mexican is a nationality,not a "race".The present racial population of Mexico(located in north America)is 60% Mestizo(of mixed White & American Indian ancestry),30% American indian,9% White(of pure White European ancestry),1% other,which includes Black Mexicans and Asian Mexicans.