[jb]

Hi all, the variety was Arran Victory, no external signs, I dont know how many yet as i am eating each stored potato in rotation which is six different types.

Last year my Arran Victories often had purple pigmentation in the flesh and were fine lasting till late winter (when they were all eaten). I assumed that it was natural as it was random, didn't affect the taste and was just like the purple in the skin.
This year I grew Shetland Black that have similar purple skin and taste to the AV's but have very pronounced purple colouring in the flesh as a known characteristic which to me suggests that the flesh staining might be something  that can develop in purple-skinned spuds.
Rather sadly boiling and baking destroys the colour in Shetlands giving pale grey flesh but roasting preserves it so we are currently having purple roasties 

[Iain@JBA]

If the potato has brown inside it I would suggest it is starting to go bad. Brown is always a sign of something going wrong with a potato.
Our saying is - if its brown chuck it out - as the potato will only get worse.
We have lots of potatoes that have colour inside but brown is not one that you want.