Hmmmm... Interesting question. I think you would have to be a bit more specific. There will always be some color changes associated with dead or dying tissue. However, they are not always blue and not always easily visible.

What I think Nathan was struggling to imply is that everybody who dies is cyanotic. I think, for example, you would want to separate a color change from something like peripheral cyanosis from a color change due to something like livor mortis or livedo reticularis. They are very different things caused by different actions in the body and appear different.

Then there is the whole notion of skin differences between people (and I'm not just talking about skin color). So, you could have 2 people sitting next to each other, both equally hypoxic, and have one person appear obviously cyanotic and the other maybe just a bit pale or blanched.

It is not unusual at all, however, to pronounce somebody dead whose tissue is better oxygenated than all of the live people around them.

So, you have two different issues (leaving out the whole issue of temperature and other environmental variables).

1) The variability of individual skin types to reflect color changes of the tissues of the body

2) Different color changes caused by different process happening in the body. (some causing blue discoloration, others causing different color changes)

Also, you have to remember that these changes are going to be more visible in some areas and invisible in other parts of the body.

So, I would say that, unless you are going to call any color change in any part of the body at any time for any reason, "going blue", no, all dead bodies do not eventually go blue.

Take, for example, one of the most common causes of death in young people (trauma) and mix it with the most common time of year to see it (summertime -- implying nice tan bodies) and you can find dead bodies in any ER in the country that look better (and less blue) than just about anybody reading this post right now.