Add the colored marker facedown into a reusable container.
Add water to each container.
Let the marker soak. (this doesn’t take very long, but the longer you wait, the stronger the color)
Use the new watercolors for mixing in a sensory water bin or paint on a canvas.
Notes
Will the water turn brown? Of course. My boys were all pretty excited and couldn’t wait to dive in. Remember, children need an opportunity to mix colors and see for themselves. They grabbed a few funnels from our outdoor sensory supplies and immediately got to work in their "coffee shop."