Decorate a black shirt with your favorite slogan or an artistic drawing, or simply add splashes of color to make the shirt stand out. Fabric paints are easy to add to most shirts with a paintbrush, spray paint canister or the squeeze tube attached to the paint bottle. Choose fabric paints that are white, fluorescent or contain glitter. These will show up better on black shirts, and so will spray-on metallic paint available for fabrics.
Wash and dry new black shirts several times. Fabric paints will show up better on slightly faded black shirts rather than brand new ones.
Place the flat cardboard inside the shirt so the paint doesn't seep through to the other side.
Add one layer of fabric paint to the black shirt, wait for it to dry, then reapply. Several layers of fabric paint will stand out better than one layer.
Attach iron-on decals to the shirt that are lighter in color, then apply the fabric paint to them if the paint isn't as bright as you want on the black shirt.
Turn the shirt inside-out to wash it after applying the paints, or consider hand washing it so the paints don't fade.