I think cutting the red
is best here. Your main goal here should be to get another another ryanmen wait. The
shape is the most valuable towards this end and cannot be discarded. Comparing the doras
and
,
is more valuable since
has overlapping effective tiles with the
wait. Comparing
and
,
has 2 more tiles for good shape and drawing
is not bad and gives a chance at sanshoku (and option to call for tenpai).
Also, drawing the
gives you worse 1 shanten shape because of overlapping effective tiles.
Discarding
to fixate on sanshoku is a mistake since it will worsen your 2 shanten shape a lot.
There is no need to sacrifice tile efficiency for value here, since your hand already has a lot of value, probably riichi pinfu dora 1 is the minimum, and there is also kan dora in play.
Edit: looking at this more closely, drawing
gives you insane good shape 1 shanten, so I change my answer to I don't know
all look pretty even to me now.
Looking this over for a long time, I think I would discard
, my thinking is drawing
after tossing
or
is not that great anyway, while drawing
or
after discarding
are not complete backfires (but still pretty bad). The backfires for
and
would be more painful I think, keeping in mind they're both dora also. In addition, if I discard
or
and draw
, most likely
would be the next to go anyway. This is a difficult WWYD, and I don't think there is a clear cut best discard.