1. Magenta is softer than purple. It offers the most traction of those listed.
2. Cyan is a Magenta with a thin harder ring of foam on the outer edge.
3. Indigo is a Magenta with a slightly softer ring of foam on the outer edge, as compared to a Cyan. More bite than Cyan, less than Magenta.
4. Purple is harder than Magenta.
5. Plaid is a Purple with that thin hard ring of foam on the outer edge, just like the Cyan.