This image was sent to glaciologist Thomas Allen Neumann.
Here is what he wrote about the coloration of the iceberg …
It’s too red to be oxidation (like blood falls in Taylor Valley). The debris loading isn’t particularly extensive (the apparent slip plane is interesting, or perhaps a former water channel), but the color is usual. Red algae would be a good guess. Two colleagues have also seen your photo and suggested the majority of the debris was from, ah, biological activity. Specifically, they suggested the reddish appearance may be due to walrus excrement. That would explain the color, but perhaps not the discoloration along the band through the iceberg.