Key

Can anyone tell me which color wire I conncet to to my blaster I'm trying to use a Honda 450r 2005 key switch

not sure you can do that, machines with batteries, starters, ect. the key is "normally open" in the off position and used to "disconnect" power to the starting and igniton circuts in the off position.

a blaster keyswitch is "normally closed" in the off position and used to "connect" cdi power to ground, effectively shorting out the ignition to stop the engine.

you may be able to use an ohm meter to find a switched set of contacts on the 450 switch, then connect our black and black/white stripe wire to it,
but.....off position will be on, and vice versa.