Watercolor paper comes in big sheets 22" x 30" inches. Often times we trim down the big sheets to paint a bunch of smaller paintings. There are times when I do not want the company's huge watermark showing up on my paintings, so I will trim those off too.
What are we left with? A bunch of little scraps.
Save these little scraps. They can come in very handy for testing colors and choosing colors for a painting. You can use them to see how the colors you have chosen blend together and mix to make more colors. You can use them to make a swatch of colors used in a painting that you will not be able to finish in one sitting. Paint a little square of each color and label the colors with a pen or pencil. That way, when you are ready to start painting again you will know exactly which yellow, red or green you were using.
Save your scraps!