Blue apples are just... pretty much worthless, as all they are is a tribal berry sold to an NPC and bought back.
Most of the other coloured food-rares date back from years and
years ago, where as the blue apple is still quite a recent thing.
I personally thought it worked still actually, but i went to try and failed!
An apple is worth maybe 25-50k tops imo, while other coloured food items could reach 1m perhaps (blue bread, purple leg of lamb, purple wine e.g.) and yet another category around 5-7m (event item coloured foods like the asian ice white apples, peaches, pears).