I know beagles are sometimes born with blue eyes but does anyone know when they change colour (at what age)

There seem to be 2 sorts of blue eyes. One, the smoky, slaty blue of the eyes when they first open, and which should have changed to brown/amber by eight weeks, although they will still darken over the months; and the bright, pale blue seen in some particular colours or breeds; collies, huskies etc. They occasionally occur in dalmatians and in that case are linked with deafness and a blue-eyed dal should never be bred from. Eyes can also be particolour - part blue and part brown.

I have never heard of blue eyes in beagles, though I expect it may occur - I would expect the normal dark, melting brown eye to be evident by the time the pup is ready to go to its new home.

The eyes were a dark blue could this mean it is not a pure beagle it seemed to be apart from the eye colour

How old is it?

He is 5 1/2 weeks

If they're a very dark colour now then by the time he's 7 weeks or so you should be able to clearly see that they are going to be a good rich brown.

Edit: What are the other pups' eyes like?

We were only shown two puppies the other was a tri coloured bitch she had dark blue eyes also.

Go and see them again at 7 weeks. I should think you'll notice a change by then. :)