Monochromatic color means using only one color and different shades of that color. Imagine if you had a favorite crayon, let's say it's blue. You would use different shades of blue like light blue, dark blue, and medium blue to color different parts of your picture. Monochromatic colors can make things look really cool because it's like using all the different versions of one color to make it look even more interesting. So if you want to make a picture using just one color like blue or green, you can use different shades of that one color to make it really pop!