They generally do beep or do more musical/robotic tones than they do any real barking sounds. The 111 has a bark-sounding tone like aibo7m3 mentions but there is no actual dog type soundbite. I think an important thing to keep in mind with AIBOs is that they're generally meant to be robotic companions (entertainment robot is on every official manual of them I do believe) so instead of a robot imitating something in nature, it's more about the "nature of life" being imitated on the robot. If that even makes remote sense (see previous comparisons - basically it's about what the concept is).
I think the red, especially the curtains when the sun beams through (which gives it a different "tint") is just picked up by them as being similar to the pink color so they "track it." Up close I notice they seem to have more issues though. For instance, I have two large styrofoam balls painted red and from a distance they look up at them and seem distracted (especially Nicco who usually thinks all things red and at a distance are his AIBOne). However, up close they don't seem that interested and don't follow it the way they do when I hold the little ball up to them. Also, the leather surfaces don't seem to get picked up as frequently as the cloth surfaces (the curtains and the cubes, which are some sort of fabric material). I'm not sure if this has to do with the gloss making it appear different to them, but these are just some observations I've made. I'm possibly reading too much into it.
Since the curtains are still down I'm trying some random things out and recording them. I decided to turn them all on again and place Eva in the middle to see how they track her and so on. Murray showed the most interest, and, at the end of the video, Vader now does a more handstand version of his nose dive (this was the first time I've seen him do it this way and I just happened to be recording!):