There were many versions of the Quad VFX over the years, and the current one feels unsatisfactory. It's not prominent enough, *especially* when a red team player has the Quad.
So, I propose this: instead of mucking with the player skin, which is hard and often leads to nowhere, make the *weapon* glow. Glow *very* bright, with the only colors it could have being brightest cyan (R0, G255, B255) to pure white. Could be done via shader or a separate set of weapon textures (which would give greater control).
This requires some minor tweaking of the lightning gun, to make its normal state darker blue with darker electrodes, and switching its VFX to pure white -- my another pet peeve, as it's often confusing if the blue glow of doom is from Quad of from the LG 'muzzle flash'. There should be *only one* blue glow and that's Quad.
Additionally, there could be a ghostly bull/demon head with angry glowing eyes overlapped with either the weapon, or the player skin head, whichever suits better. It would require only one, non-animated, model with one skin, but the look would be pure badassery -- and no more confusion. You see the glowing horns and eyes, you know it's time to shit bricks
A gaping toothy maw around the weapon muzzle would be a fine variation too.