The colors on the border of the gauge are basically just for aesthetic purposes, indicating that the gauges are being filled. They have no other real purpose than that. As for the aoe, it seems to me that you want to primarily do Scatter > Dualcast alternating main Ver-spells, so as to help supplement your gauges and wear down one foe faster than the others to help relieve the tanks/healers. Then when you've built up your mana enough, use your E. Moulinet. When you're dealing with 3+ mobs, you basically want to ignore the procs completely until the mob number drops back below three. Don't forget to weave in Contre Sixte too whenever it's ready. As for how many E. Moulinets to use at a time, this was something I was rather curious about myself. It seems building for the maximum three is the consensus here, at any rate.