When introducing a new concept to the class, sometimes I like to use some sort of game. That helps the students retain the information better, gives them incentive to learn the material, as well as gives me immediate feedback as to whether or not they understood the concept.
I learned from a fellow teacher that our blackboards are magnetic (yay!) so I punched out paper circles with a die-cut, and painted some, and used colored paper or colored pencils for others. That way I got an array of different colors. I put magnetic strips on the back of all of them, and when I greeted my 2nd graders at my door this morning, I gave each one a colored dot.
Then, I introduced the concept of warm and cool colors to the class, and had them all put their colored dot on the left side of the board if it was a cool color, and on the right side of the board if it was a warm color. To my delight, everyone seemed to understand very well, so we started the project. 2nd grade is making desert pictures with the sun setting, so everything will be colored with warm colors. Once this is done, they will make a picture using just cool colors, but I haven't decided what yet.