In a game, I had potted a red and was in a position where I was unable to hit any coloured ball directly.  When I tried to aim at a colour off a cushion, the "ball on" was shown as a different colour to the one I wanted to hit.

So far as I can see, there is no way of either a) locking on to a particular ball or b) changing the colour of the Ball-on.

Thus, for instance, I wanted to hit a blue ball via a cushion, but it was showing black as the ball-on.  IF I had hit the blue ball, it would have shown a foul.

What is the solution please?  I would like to know how to do it.

Thank you.