Assuming you want to remove paint from a decal:
There are a few ways that you can remove paint from a decal. One way is to use a razor blade or a sharp knife to scrape the paint off. Another way is to use a solvent such as acetone or alcohol to dissolve the paint.
If the decal is made of vinyl, you can also try heat to remove the paint. Use a heat gun or a hair dryer on the highest setting and hold it about 6 inches away from the decal. The heat will cause the paint to soften and you should be able to peel it off.