How do I prevent wrong totals adding to score variable?

I'm creating a test of a game whereby the user must hold down a button which will shoot a ball and they must hold the button for the right amount of time so they get the ball to land on the target. The scores are as follows:

Green circle - 2 points

Yellow circle - 5 points

Red circle - 10 points

What I'm currently doing in the events is comparing which object the ball is overlapping to determine how many points are added to the score variable. However, when the ball is over the red circle for instance, it's adding 17 to score as it's also overlapping the other two circles.

Is there a way to get around this?

Create some kind of loop that checks if overlapping red and if so then add and stop the loop, else check yellow, then green.

What should I use as the start and end indexes?

If you want to use overlapping, make sure to add a "pick top instance" condition. Howevever, BadMarios suggestion is more accurate, since it doesn't have to rely on collision polygons.

Cheers for your help guys - I've managed to get it working right by using distance from the centre. Really appreciate it!