so when you want to color something you use the fuzzy tool to select it and then you can either new layer the plaid and put it behind the main layer. When you do this you click the eyeball on the main layer to get rid of it for a while the fuzzy part is still highlighted, you then go to edit and click copy visible. After clicking that you click on the main layer and reappear it. You then go to edit again and click on paste and it will open as a new layer you then right lick that and open as new layer.
or you could open the paid up and go to edit and copy visible and then paste as and save it under pattern then go to the layer with the kisekae out and fuzzy tool over the pants and click and drag the plaid over the pants and drop.
((Hopes that helps I kinda suck at explaining things over the internet ;A; ))