I would agree with esoomenona's classification of weight. I don't have a huge sample of different springs to compare against, but here's a picture of a spring from an unused clear, and a spring from a grey I pulled from an old g80 8113.
The reason why I said I don't feel much of a difference between clears and greys (though I did mention that the grey felt stiffer overall), is because of the drastic increase in force in the clears after actuation. Yes, the greys are stiffer, and from the spring (singular) I have, it is perhaps because it seems to have been electroplated over with something else, judging by the color of the spring.
To my fingers, the force difference needed to actuate clears might be a little lesser compared to the greys, but after actuation, it's a different story - see the difference in the number of coils in each spring and the difference in overall height.
The more active coils, the less load you will have to apply in order to get it to move a certain distance.
But accounting for the unactuated starting height in the grey and the possible plating/material difference, it would fit with what the wikis are saying - 80cN for the greys over 65cN for clears.
But after actuation - the clears are said to rise up to 100cN in resistance, apparent in the design - shorter springs, lesser coils etc. It is something you can consider in creating your heavy greens.
I have no idea how much resistance the greys have after actuation, but they feel pretty similar to me at that point, though the greys are probably heavier prior to actuation.