Make muscle coloring (e.g. excitation, activation, etc.) more sensitive for lower values

[adamkewley]

Reported by TvW

When muscles are excited/activated with lower signals (e.g. 0.2), it isn't very visually obvious that anything's going on.

Technical explanation: the current algorithm of LERPing Blue -> Red based on the coloring factor isn't visually sensitive enough and might require also going through some kind of easing/transform function (e.g. log it or similar).