Can someone please tell me the difference between the two. I have bought a blue staff recently and don't know which she is. Are all blue ones irish?

In answer to your quesiton no not all blue Staffords are Irish bred just like not all brindles or blacks are KC.  Blue is just a colour and as you know Staffords come in all colours.  There are a strain of Staffords that come from Irish stock hence the term Irish bred Staffords but dont be fooled into thinking they are a seperate breed, they are just a variation in type.  There are a few lines that commonly throw blues.  If you have an Irish strain Stafford you must have papers for it telling you which lines it comes from.  If the dog has no papers it is not an Irish bred Stafford just like if it does not have papers it is not a KC Stafford either.  Irish is not a type (i.e. it does not just mean a leggy Stafford): it refers to certain lines of Stafford bred carefully for many years for sporting/working purposes and now bred for athletic events like weightpull etc.  If your dog has no papers what you most likely have is a blue unregistered SBT just because it is tall does not make it Irish bred nor does a small dog mean its KC.  The only way you know for sure whether the dog comes from Irish or KC lines is if it has papers if it does not it is more than likely just an unpapered unregistered Stafford nothing more nothing less.  Does it really matter anyway.

In answer to your first question I am going to copy a reply I made to a different post as it saves me typing again and may be of some benefit to you:

Generally the Irish bred dogs are seen as taller and more athletic, but I would just go for the reasoning that really they tend to be more athletic in looks coming from working stock you find that they are built more for speed, stamina and power with leaner bodies and longer muzzles with less wide heads and more obvious musculature from rigorous exercise, they are in many cases representative of Staffords which were around at the turn of last century in general this is the aim of most people within the breed, not to create a different breed altogether but to revert back to the way the dog once was and to give potential owners the choice of varying types within the one breed.  It should be pointed out here that there is no breed called the Irish Stafford there are strains of Stafford that come from Irish stock hence the term Irish bred Stafford or Irish strain SBTs but many people make the mistake of putting the two dogs in two different categories.  There are a few lines that run taller than others but in general they are usually only a couple of inches taller than the current UK SBT standard the main difference is the weight ratios which were not amended when the standard height was brought down by 2". 

As with any dog do your research and learn about the various lines, well known breeders, health issues within the breed what type you like what lines you prefer and most of all don't rush.  There are just as many bad breeders or Irish dogs as there are any other type of dog.  If you have the right knowledge you should have no problems in finding a well bred Stafford from Irish lines, also there are many KC lines which run slightly taller and are known to be more athletic than some, Yankeestaff is just one name that springs to mind there are many more.  The best you can do is gain as much knowledge as you can and hopefully by the time you come to look at some dogs you will be familiar with the various lines and pedigrees and you will be able to make a better informed decision on whatever dog you choose.

Please note there is no such breed as Irish Blue or Blue Irish SBTs as some people have come to think in recent times the colouring is merely a diution of black and is very common within a certain strain of SBTs namely the Kaos Kennel (KK) dogs bred down from Psycho bloodlines.  If you do decide on an Irish bred SBT please also be aware that there is an inclination for many breeders to charge extortionate amounts for colours that are seen to be "rare" i.e. blue indicating you are getting something special for your money.  Please do not be fooled into this current craze, a blue stafford is worth no more or less than a white, black, red or brindle Stafford.  A litter of blues costs the same to whelp & raise as a litter of any other colouring.  Moreover, I would say a reasonable price limit for a stafford would be £400 usually the norm between £300 and £400 the tendency to overcharge for the blue colour is crazy if you look hard enough you will find good breeders who charge reasonable prices whatever the dogs colouring as they are interested merely in the breed rather than lining their pockets.

No, blue is an acceptable colour in the Staffordshire breed standard. her breed will be on her registration document. If she isn't registered there's no way of knowing.

"If she isn't registered there's no way of knowing"

You managed in about two sentences what I wanted to in about three paragraphs lol.

;) :D