Felt-tip or permanent markers will smear when Metro applies the protective coating. Acrylic paint pens or small paintbrushes can be used for outlining, but make sure it doesn't look like graffiti. Large, flat areas of color can attract graffiti. Large, one-colored areas and especially large white or yellow areas can attract graffiti. Breaking up large areas with a design, or blending colors reduces the chance of vandalism.
Words can attract graffiti and words can be perceived as graffiti.
If you want to include words or phrases in your design, paint them neatly or in a creative way that won't attract graffiti or be perceived as graffiti. Avoid using questions. Questions beg for an answer, and someone might answer it with graffiti right on your mural. Including a short poem or quote in colorful designed script can add a very nice touch to a mural. Simple brushstroke lettering, if not done carefully, may be perceived as graffiti that was added to your mural.