I'm assuming that the damage to the comb is from having been poked and prodded by a hive tool, otherwise there's a problem with how that comb looks regardless of the color.
If the comb looked normal other than the red color, I'd say it's just hummingbird feed or some other man-made sugar based liquid that your bees found useful.
If the comb looked normal other than the red color, I'd say it's just hummingbird feed or some other man-made sugar based liquid that your bees found useful.