If you find some “purple veins” inside a potato, that’s very common; however, it would be ideal to get potatoes without green spots, brown spots, pink flesh, and of course, without purple spots or any veins.
The truth is that no vegetables are absolutely perfect and that includes the potatoes.
About your question, I see you didn’t mention if it was a Russet potato or any other variety. Or if it was only one potato, or you have some more and haven’t noticed if the rest of them have “purple veins”, too.
Or if you were growing your own potatoes. In fact, the variety isn’t a concern right now, but my recommendation is this: Do not eat the potato if it has deep blue or purple “veins”.
Some potatoes can have a pink or reddish color inside, which can be normal.
It’s also very common to find potatoes with a green color under the skin. If that’s the case, it’s not safe to eat those either. I will explain you why.
The green color comes from a toxin called solanine. Because of the solanine, potatoes can turn green when they are exposed to sunlight. And if that’s the case, you could throw it away.
Why is the potato purple inside?
If you find a Russet potato (or a variety other than purple potatoes) with purple spots or veins, while the rest of the potato is white, I would say that it’s not a good idea to eat it.
Some people argue that nothing is going to happen, and if you ate already it, it’s possible that nothing bad is going to happen.
But eating a greater amount, let’s say for example that you eat two or three potatoes at once, and this is only my opinion, it could make you sick.
Because you don’t know if the potato got that color from a change in temperature at the time of the harvest, or from a chemical or even a fungus.
If the purple spot is small and you don’t want to throw the potato away, just remove the damaged area.
And just to add a little comment: purple spots or veins can also be found in other vegetables like peppers and tomatoes, not only inside the potatoes.