Poision skill grows now faster per upgrade(*1,81). thinking it might outrun yellow for (very) high lvl gems.. also we might need a new upgrade method for green...
16 grade combining with a black green red gem i get 20 times more poison.. but since y/dmg grows by 2,2 and green just 1,8 for a normal U upgrade... maybe as a fourth component for yellwo/black/red?
A fourth component is still boosted by that one skill, it is when you get a fifth (or more) color components that the skill loses its value. Of course, you are paying for it by reduced specials ...