Blackberry is a Green food. Green foods are safe to eat as a regular part of a diet.
Guideline related quotes related to Fruits-Low-Fructose-Low-Glycemic and Green throughout Geoff Bond's publications.
Eat at least six pieces (servings) of fruit per day, focusing on “Green” and “Green-Amber” fruits. ~Paleo in a Nutshell p.102
Restrict total fruits consumption per session to three servings. ~Paleo in a Nutshell p.102