The blue car is waiting at the stop sign. This means that the driver must give way to all other vehicles before proceeding.
If both signs are stop or give way signs, the give way rule applies. In this case, the blue car has the right of way because it is going straight. This tricky situation (which is not well explained on the New Zealand Transport Agency website) may catch you off guard: always remember that if you are at a stop sign, you are the last person with the right of way.