A blue ink pad really isn't the best as it takes ages for the blue ink to dry.
Though I would recommend getting a very large BLACK one from the guy you will meet as you walk into the hall - he sells cards ink pads almost any coloured stamp pads and dont forget to get his meet stamp
However the official stamp is just about as far away from the door as you can get in the opposite corner (to the left of the people queueing to get their membership of the 100 letterbox club and both queues tend to get mixed.
Colour in the stamp world is the spice of life
Although I detest those emulsion based ink pads as they clog up the stamps
Best one I ever got was a stamp that could only be used with a white ink pad - so out of my box produced a black card!!!!

It was meant to be a joke but I managed to turn the joke around