My kids did a similar thing - only at least it was outside and my TV wasn't involved.
I left 4 litres of stain out (I was staining my treated pine retaining walls) and the kids painted the side of the house, the bushes and each other with it. Initially, I nearly drowned them in the toilet but I realised the following:
1 - Who was the idiot that left the stain out,
2 - Who encouraged the kids to "help" while I was staining the retaining wall,
3 - They did a near perfect job. ;-)
So, I would say laugh, then cry later when the cleaning up starts.