TL;DR:
red>orange>purple>blue>green ALWAYS
keep your orange + nin/atk pen and injury in inventory
Your exp/stat *ysis is wrong. Not in the numbers but in the method.
Specifically, you should not compare it by level, but by experience invested.
Take lv 11 purple, for example, it provides 239 nin for 8964 exp.
For less exp, you can have a lv 8 red, which is 387. Ergo you have more stat for the experience.
Instead, you should compare at exp benchmarks, for example:
100 invested
200 invested
400 invested
800 invested and so on. (since exp required grows more or less exponentially, power of 2 for a chart is a good way to go, 68256, which is the max for red, is only between 51200 and 102400 which is 10th and 11th step after all. Granted, if you just try a few numbers, you will see that higher color is better making a full chart moot)
And you c*e partial levels to give an exact comparison.
For example, take 800 invested on nin, this would be
green 7 + 60/320 = 43+1.125=44.125
blue 6 + 224/312 = 81+8.615=89.615
purple 5 + 296/360 = 125+15.622=140.622
orange 4 + 296/504 = 165+15.270=180.270
red 3 + 368/576 = 217+21.722=238.722
Clearly, for 800 experience invested, red is far better.
After all, experience is our limiting factor and comparing a lv x purple to a lv x red is moot, instead what matters is what stat you can get for a lv y red that you can get for the exp it took to get a lv x purple.
That said, your current chart does have its uses, in that it helps us determine what rune to level next.
Specifically, it goes like:
2 purple, 2 blue, 2 orange, 2 green, 3 purple, 2 red, 3 blue, 3 orange, 3 green, 4 purple, 4 blue, 3 red and so on. This helps us get the max stat out of all our runes for the same exp.
As for the useless stat, while injury is far too bothersome for me to test, I did do a limited test on the *ion and can confirm that it have no noticeable effect. That said, I expect them to have an effect eventually from a fix patch, because they SHOULD, so I'd keep the high colors in inventory all the same. I agree with OP, however, that they should not be used at the moment.