Males and females may behvae differently at this point. As stated, females will most likely lay eggs and tend to those eggs for the duration of her life being very reclusive. Males in senescence may be very active about the tank, much more than previously in their life.
Autophagy, epidermal sloughing, and decreased appetite may also be signs of senescence. I have not observed much in the way of color loss at this time.
It is also good to keep the specimen's age and size in mind, if at all possible. These same symptoms may be exhibited in younger octopus due to various other reasons.
Greg