Homemade Sausage Making

I see some darkened color on my sausage. What is this ? Why it happens ? Is it safe ?

I appreciate the input from masters.

At this point I would not be concerned, it may have been touching something or just drying unevenly. We need more more info about your process.

Did you use some variety of red pepper flakes? I just made some calabrese and had the same concern until I realized it was just pepper flakes that had not been crushed finely.