George and Lynne are paintballing. Lynne tells George that Minnie held a paintballing party in her house for her kids. George thinks that was a bad idea. Lynne continues her story by saying that by the end, every wall of her house was covered in paint but it is one way of redecorating your house for free.
Paintballing is usually a group activity but George and Lynne decided to hire out the entire complex for themselves, presumably at a massive cost. Either that or they have broken away from the main group to release some tension from their relationship.
Whoever loaded the paintball guns has made a bit of an error. Lynne has been firing yellow pellets but at the end she fires a red pellet at George. He is 'killed' in the game but when he goes back to base, the person keeping score will ask who from the red team shot their own member.
The same person who loaded Lynne's gun is probably responsible for letting a children's party use the guns indoors. Lynne is not right. It is not a good way of redecorating your house for free. For starters it wouldn't be free as paintballing is quite expensive. Secondly, unless you want your house covered with yellow and red splodges, your house will look an absolute tip.