Gas combustion made simple! At about 10:1 air / fuel you will get a nice blue efficient flame (natural gas, propane not so much), plenty of oxygen for efficient combustion. A nice blue base of the flame is a reasonable indication of an oxidizing fairly efficient flame so the answer to your question is basically yes it’s a decent indication enough primary air is coming in. . Venturi burners are sort of self calibrated within a pressure range of operation so the more gas pressure, the more primary