I believe we have a little bug 
in the system.
Try this example aia project
binman.aia (3 KB)
It should work as expected if you drag the black ball onto any of the other coloured balls (and let go - touch up).
However, if in the blocks, you remove the Ball4 visibility blocks from the Touch Up event, whichever ever coloured ball you drag to, the colour blue is returned.
I will now have a look at your project....