Creating a portrait is the perfect way to practice recreating what you see in real life, on paper. Have someone sit for you, as you draw their portrait (typically the face and the top of the torso) from life. If a model is not available, use a photograph. This can be done in any medium, but a good way to begin is by outlining the figure in graphite, then going over it with paint later on. Portraits also allows for visible results and progress, as you can always look back on the portrait and review your accuracy and style, and how it has changed with practice.
A selective color painting allows the artist to focus on color and mood, and how they often work in unison. Choose a color, and think about what mood it immediately evokes in your imagination. Then, create a painting using solely that color, to represent the mood. The painting can be either literal or representational, as the goal is to represent your personal take on the color. If this activity is done in a group setting, present your paintings to each other and have a discussion about what each piece means to the group members. It will be interesting to see how one color can hold vastly different meanings to varying individuals.