What speaks to you? Crfayons? If so use them. Do you only like to write in blue, purple or green? That's okay too.

Do you like:

Sharpies?
Caran d'ache?
Charcoal?
Acrylic?
Watercolors?
Colored Pencils?
Collage?
Gouache?
Ink?
Rubber stamps?
Pastel?
Watercolor Pencils?

If so use them.

Do you hate any of the above? Then don't use it.

Do you like to use more than one? Use whatever you like. Mix 'em up.

Use what you like there is no one (but you) to stop you!