Do you know the difference between paint and stain?
Paint is stuck on the surface, and if its really good paint it sticks tighter than most other paint. But stain goes down deep; it soaks right into the wood or the concrete. And even if you scratch through the surface, the stain still shows.
Sometimes we think we want a good paint job from the Lord, and thatll cover over the bad things and the imperfections in our character. But what God is asking for is that we be changed deep within, that we be stained with the blood of Christ.
That paint job may wear pretty well on Sundays, but in the real world the scratches and cuts will show what runs deep and what doesnt. Outsiders can look at Christians and tell the difference, just like you can tell the difference paint and stain.