what do you mean by anxious? Do you mean nervous and shy or constantly active? Most breeds of hound are extremely high-energy dogs needing lots of exercise. GSDs also need a good amount of exercise to keep them healthy.
I am not sure what you mean, I love red. I have more red mini aussies than black/blue. They all have about the same temperment from what I see. I did notice red standard poodles I have groomed seem to be calmer then black and white ones.
The mix you have is a very high drive, and loads of energy. He is probably just being the dog he is.
No, this is not something that is present in any red dog. Color has absolutely no bearing on a dogs behavior. This can happen in ANY dog, regardless of color, and would be based on level of activity, excercise, mental stimulation, socialization, etc.