The blue is the Pokémon's original stats (75 base HP, 114 base SpA, etc.) while the yellow is the Pokémon's EVs. Yes, the game refers to them as base stats, but they are actually EVs that can be modified. You gain certain EVs by fighting certain Pokémon, and you can get ride of EVs with special berries or a Reset Bag.
TL;DR The blue is your Pokémon's base stats, which do not change, and the yellow is your Pokémon's EVs, which add points to the base stats and can be modified.