So, without testing (Too tired) I did some online digging... Xun and I have been discussing it on and off and weren't sure of all the options. Well, like shopping, the best things catch my eye
Here is all 8 modes ripped from an old RunUO post from like 2004 or so.
0 = regular hue chosen without any change.
1 = creates a 'black' effect that when it hits the target, becomes a black outlined, transparent dark red/transparent ball of fire, not matter what the original hue chosen is. (the ball of fire is due to my own choice of explosion end effect)
2 = creates a slightly transparent end effect in whichever hue you have chosen. There are no shadows in the effect (aka no black at all).
3 = appears to be the same as 2.
4 = like 2 and 3, but with a little shadow in it (aka a little black to add to the demension of the effect).
5 = more transparent, and more black shadow.
6 = transparent and black regardless of the hue that is chosen.
7 = more true to the hue chosen, but dark and transparent. I would say that it has more contrast between the hue and the black shadow-like quality.