If it’s any help, here is some code from one of my projects. Takes start and end hex colours and the number of colour steps you want to create. Then you can use steps(step) to get the hex colour code for that step.
http://pastebin.com/enVzwUSP
I happen to have stumbled across https://atlas.ripe.net/results/maps/comparative-dns-root-rtt whilst working today. So, it’s just finer increments which may be better.
I guess that is the question, do you need 1 minute resolution forever?
I wouldn’t see any issues storing data in RRD and configuration/current status in MySQL.
Check out RRDtool, it was made for this sort of thing. It’s a very simple and robust tool.
If you want a circular buffer with SQL support, then MySQL really isn’t the tool. PostgreSQL would be your best option.