A throttle with red, green, and black wires is a variable speed throttle and the original Razor E300 throttle with two orange and two brown wires is a single speed throttle. The variable speed throttle cannot be used to replace the single speed throttle because they are two different throttle types.
Either a single speed throttle with the same wire colors as the original throttle will need to be purchased, or a variable speed controller could be purchased and custom installed on the scooter if you want the scooter to have variable speed control.
Please let us know if you have any questions.
Jim krebs