{Garruk Relentless}
I understand that the back side of the new(ish) flip cards count toward color identity however I have heard debate as to if his flipped form is black or not. As a colorblind player the symbol color/base color on the card are of little use to me.
Also as a colourblind person, I understand how this can be tricky.
As you have already mentioned, both sides of the card count towards its colour identity.
From the front, you have a normal green card, as identified by the border surrounding the name, the picutre, the card type and the text at the bottom. (the thin line)
From the back, we have the same tell tale border, and an aditional colour identifier next to the card type (planeswalker) this is found on all flip cards, even the mono ones.
This identifies him as a Black/Green card.
I hope this helps. :)
Thank you very much.
711.2. Each face of a double-faced card has its own set of characteristics.
711.2a In every zone other than the battlefield, and also on the battlefield with its front face up, a double-faced card has only the characteristics of the front face.
711.2b While a double-faced permanent's back face is up, it has only the characteristics of its back face. The back face doesn't have a mana cost; it has the colors in its color indicator (see rule 202.2e), if any.