Just file this away for future reference...
If the day is very, very hot and your children are at loose ends, and you happen to be at the craft store picking up a few more supplies for your preschool curriculum, do not under any circumstances also buy your developmentally older children paint-by-numbers to pass the time. Do not do this even if the disregulated child you have with takes a sudden interest in them and thinks it looks like something he would enjoy. Just turn around and make the few purchases you actually came for.
Because if you don't, you will be reminded how dreadful it is to deal with a frustrated child who is an extreme perfectionist. And the fact that the painting does not look like the picture, even though only four spaces have been painted in, will undoubtedly be your fault. Your fault for allowing him to choose an obviously defective kit. Your fault that the colors do not match exactly. Your fault that he cannot paint like the computer generated image. And when you try to help him, he will get angry with you all over again.
It will not turn out to be the fun distraction you had planned.
Some days you can't win.