You need a circuit tester (test light) to confirm power and ground to the relay. Do you have one or can you get one?
white/green is power in for starter should be + constant
black goes to starter should show - normal but + with key in start
white/black is constant -
b/r assuming black/red but could be blue/red is + from key switch.
Cover snaps off around radio for access and should be on left side of radio. Seems like mine is green.
This diagram may help, it cuts off the battery pic on left and ground on right.