In Kotlin,you can use using alpha like this,
//Click on On.//
view.rel_on.setOnClickListener{
view.rel_off.alpha= 0.2F
view.rel_on.alpha= 1F
}
//Click on Off.//
view.rel_off.setOnClickListener {
view.rel_on.alpha= 0.2F
view.rel_off.alpha= 1F
}
Result is like in this screen shots.
Hope this will help you.Thanks