HIVE

Wow thanks! How did you found out those numbers? Trial and error (+ comparison)?

I captured the Banish and Flame Strike icon in game both castable and not enough mana. I then compared approximately the same pixels between the two. Blue channels were unvaried, with at most some difference in sub pixel bilinear filtering. Red and Green on the other hand were drastically reduced and since this effect must be performed in real time it could only be a linear reduction. I tested this theory by using an image editor to reduce the red and green component values of the castable icons by the guessed amount and then analysed the difference between the resulting image and the not enough mana image. The result was a 1 pixel noise meaning rounding error (possibly from bilinear filtering) but same generation logic.