Chalkup lets you customize the color and icon, here's how you can set it up.
Choose one of your classes in the left sidebar.
Click on the course name, and choose "Course Info" in the dropdown menu.
Then, you will see a list of colors available for you. If you would like to add an icon, click "Choose icon", and you'll see all of the available options.
When you're all set, make sure you click "Save"!