I don't know. It's weird looking at them. The only one I would call well defined is Enchantments in G/W...or at least obvious. B/R does seem to profit from a sac for value theme, but it looks a bit flimsy. Black and Blue have a mild mill/rez theme.
You know what...it seems like Four-color synergy...Single color matters and you should be using two to three other colors to support that theme...
Green has Elves and is supported by White with an Enchantment theme, Black with Elves, and Blue with graveyard (Wonder, Brawn, Threshold).
White has Weenies (tokens) and is supported by Enchantments in green, burn in red, and Control/Fliers in blue.
Red has Burn and is supported by removal in Black, Flashback in Blue, and efficient Beaters/Threshold in Green.
Blue has Control and is supported by Removal in black, Removal in white, and Removal in Red...(this could probably use some work...)
Black has Morbid and is supported by Red with Echo, White with Vanishing/and a few other cards, and Blue with graveyard.
I don't know...does that make sense? Then I guess you can build your themes from there
B/W and B/R both have some solid Sac matters synergy - White with
Soulcatcher,
Field of Souls, Vanishing...and maybe
Balance and
Wrath of God, Red with Echo for Burn and
Tooth and Claw.
Although B/W might just be all things die but then I can rez my stuff or typical high power cheapies with black/white removal support?
W/G has great Enchantment synergy...which also seem to have a tokens theme...
Field of Souls,
Intangible Virtue,
Honden of Life's Web, etc
U/R has "spells matter" or Flashback
B/G has elves
B/U has a mill/rez thing going, couple mills, couple digs, and that obvious
Extract from DarknessW/R has a suicide aggro thing, bunch of Weenies in white, bunch of expensive weenies with etb or combat support/burn in red.
W/U passably looks like fliers but looking at the commons makes me think maybe not...might just be control control control...
U/G is maybe Graveyard pump? Threshold,
Wonder, and
Brawn? Even Cascade can help get stuff in the yard...
R/G looks like my combat is better than yours? (combat tricks)
Three colors? Those cards look more like Rez targets than indicators. And I think Cascade may just be a coincidence...although I guess maybe it is the fun fringe deck this format...