One possibility would be to use a Google Drawing, part of Google Drive, if you want a more visual and easy-to-edit option. You can create the cards by grouping a color-filled rectangle and one or more text fields together. Being a sufficiently free-form online vector drawing program, it doesn't really limit your possibilities like if you use a more dedicated solution.
The only real downsides are that you have to first create the building blocks from the beginning, and don't get numerical statistics like with a more structured tool.
