You can not use Behaviors properties in expressions trough a Family. Lets accept that at this moment as a fact. Ashley added Behavior tabs to the Family's in the condition and action wizards.
Maybe he overlooked the expressions. Or he has no plans to.
Besides the fact that you can not do it the way u try, i wonder about the "why".
Why would you want to move 3 objects as they are "player objects" ? You bring yourself in deep problems in that .cap. Because, well, how to explain ?
You want conditions that are made to be a flow condition to act as a pick condition.
Flow conditions are true or false. When true they execute there sub events and actions. When false they dont.
Pick conditions pick a group of objects (can be a family), filter according the condition, and pass the filtered object(s) to the sub events and actions.
What u have there,
System: Sprite[Platform].VectorY Equal to 0
is comparing 2 values, when the comparison is true, the action will run.
Thats what it is designed for.
So the action
Blue Set gravity to 0
Will set all Blue's gravity's to zero. ALL Blues ! When the comparison is true.
You can see that if you delete the other 2 "Blue Set gravity to 0" actions.
So even if you could access the behaviors properties trough a Family, your events dont do what you seem to expect.
Of course, if the action directly addressed the object "sprite" then it would work, because there is no need for a pick event then.
But since you insist to work with a group of objects, represented by there Family, you need a pick event. The correct pick event here would be :
Blue: compare a behavior propertie. Close to the conditions we have already as there are:
Blue: compare x position ... Blue: compare private variable ... etc
Now well, we dont have that condition (yet).
So its the same problem. Yes is exactly the same problem. Moment we have the condition, expressions will be available too.
You understand ?
You have 3 instances of the same object Detector. You have 3 totally different objects.
They way you snap there X's to each other works more by incident then by design, or good coding.
Just duplicate one of the faces, as clone or as instance, dont matter. If you do as clone, dont forget to bring it in the family blue.
And before you run it, try to predict what will happen.
You see ?
3/ why promote 3 objects to "player objects" ?
4/ i would make you a .cap with a nice work around. But, in my learn curve, i did not reach the Platform yet. Because in my eyes, what use is it to not understand the events completely and dig my ass in the behaviors. So i dont understand the platform behaviour yet. I am sorry.
But i am sure, if you understand what i just told you, you will see the light and come up with a solid solution.
Although, just theoretical, i dont see practical use in 3 player objects.