Art activities can be a fun way to practice various skills, particularly if you're making a project about something a child is interested in, such as trains. In this activity, students can work on:
Fine motor skills,
Identifying colors (choosing the colors to paint with),
Following directions or following a demonstrations,
Communication skills (asking for materials needed for the project, such as the crayon, paintbrush, water, paint, paper, etc.).
As an overview, you make a drawing or trace a stencil with a white crayon on card stock or thick paper. Then, you paint over it with watercolor to make the drawing "appear."
Materials needed for the project: water color paint, bristol paper (or other thick paper), white crayon, and stencil (optional).
I'd recommend starting this project by the teacher or parent making a drawing with the white crayon and painting over it. This shows the child what will happen. Some of the kids I've done this activity with seemed a little perplexed that they couldn't see their drawings after they've done them with the white crayon on white paper. When they see the full process, they understand what will happen. You can just do a quick drawing example like this:
First, the student will draw a picture or trace from a stencil.
Then, the student will paint over it with water colors.
I used this book of stencils to make an additional stencil specifically for this project. This book is a great resource and my students enjoy making various projects with it.