I would like to add in my two cents. With the planeswalkers that we are playing, I do not feel we should worry too much about the sharing of colors. Aside from limiting creativity, I want to suggest that colors are not the issue. I think we need to be worrying about the kind of magic that color adds to the character. The more colors a planeswalker uses the more diluted those individual colors actually become.

For example, Syeena is green white and red while Victoria is black red and white. They overlap in red and white. However, their red and white magicks are night and day. Victoria is far more aggressive and destructive in her use of Red/white. Syeena (From my impression) uses red white to preserve the collective good. She uses red to destroy a threat to the group in order to preserve the whole. Victoria uses red to destroy things that get in her way without care whether that death is good for the whole or even herself. I know these are probably just personality, but Victoria uses red for its raw destructiveness while i feel Syeena uses it for its utility to augment her abilities.

Basically what I am implying as long as the magics used by the characters are unique then it should not matter which colors they chose to splash into. I confess I am completely willing to drop white mana from Victoria. Her white magic is an odd emergent property coming out of her choice of using magic talored to war and conflict. Wars are conducted between groups of peoples. White/Black tends to see the group as an extention of the individuals and Red/White is warfare where sides fight each other with the full passion and zeal of red but the group that white loves (Basically classic Boros). Victoria is solidly Black then Red as she was blessed by Theros's red/black god, Mogis.

Other then I being willing to make Victoria just black/red. I would have to comment on the mana fixing lands. I think the second option is better. Each land has the basic land type of the center color of the card yet pings you for the enemy dual colors. I like the idea. However, What if instead of you taking damage from the enemy colors, your opponent gains 1 life.

P.S. I have a buddy interested in joining this rp, however he is doing summer traveling and will not have internet for about another week. He was thinking of being an Blue white mage.