There isn't a single spring chart that I am aware of.

Tamiya tend to colour their springs to show relative hardness, but the actual rates are different from set to set. There can be multiple sets of the same size which makes it even more confusing.

What I would do is choose a set of springs to use, and tune your car using that set alone. I use the "black short" springs which are wound differently to the "white short" or "short" sets, but at least I know which spring is relatively stiffer.