Draw line in to sprite unity

I going to make a game draw & color by unity, but i dont have ideal about how to draw color just on part of sprite, not over to another part of prite. Could you give me ideal or somethings keyword, thanks for help. And i am sorry for english skill bad :sweat_smile:
image

@pdypham Do you still have issues with this?

yes, I no have ideal for this now .