No, quite normal behaviour, it's just new growth. If all the 'plain' leaves are growing off stems with variegation, leave them - if your shrub is in a very shady spot, that might account for the trouble - a bit of sun should encourage them to colour, but I'm sure they will eventually.

But that new leaf isn't all-green, Bernard.
I can see the markings on it and that paler colour is going to be yellow eventually.

I have to admit that I'm not seeing the markings, Louise.
That small leaf visible in the picture was the first leaf formed by that branch when it started growing. Since the larger leaf above--on the same stem, but off the picture--is also all green, there is a good chance that that branch has "reverted".
Reversion isn't a mutation. Most variegated plants are chimeras--that is, there are two different plants "mixed together", normal green and albino, to show the different colors. Every once in a while, the albino cells "miss the bus", and the resulting shoot is wholly from the green part. The reverse can happen, too, resulting in all white shoots, though that is more rarely seen.
The all green shoots are more vigorous than their variegated brothers, and can easily take over the entire bush, if you don't keep you pruning shears handy, Bernard.

I can see some variation on the shading on that new leaf as well though Tug - the right hand side has a distinctly golden appearance compared to the left, so I'd still be inclined to wait and see how it develops.

Still not seeing it. Looks to me like the way the light is hitting it, and the way that side of the leaf is angled more towards us, making the tufts of wool look closer together. Then again, my eyesight isn't perfect, either!
: )

That is not the angle of the light.

I have had these plants in most of my gardens over the years and it is DEFINATELY a leaf that has 2 colours on it.
The shading is definately there and WILL colour up as it ages over the next few weeks.
I'll take some pictures of my own plant in a while and let you see that this is NORMAL, Bernard.

I've just shown some foliage variations in a 'Variegation' blog, Bernard.

Thanks for that Louise1. I assume it was OK to print it out and add it to my Eleagnus file. The behaviour and for some plants is very interesting and for a beginner can lead to the wrong decisions being made. Just think, I was on the verge of cutting off all the green leaves because, in my limited gardening knowledge, I remembered the advice that if single colour leaves appear on a variegated shrub, they should be removed otherwise the shrub will lose its variegation. A little knowledge............ The members of Goy have provided me with advice which is priceless for a beginner and I can just imagine the mess I would be in if it wasn't for all of you.

Did you get my PM, Bernard ?

Yes, Louise1, I did. Thank you for it. It referred me to your 'Variation' blog which I have copied for my Eleagnus file. Your point about Tugbrethil is interesting, but it's difficult to know the nationality of the people responding to a question and even more difficult to know their level of competence, regardless of nationality. However I'm getting to know the small core of obvious experts who have replied to my questions in the past, so I feel sure that I'm getting gold-plated advice from them. I shall watch that little shrub with great interest and enjoy it even more now that I know so much about it.

Tugbrethil is a qualified horticulturalist, Bernard, just for interest's sake - but lots of things are different in America, of course.

And things are very different, here in the desert Southwest! Still, Elaeagnus is one of the few things that grows both here and in the UK, and I do have experience with it. Normally, I would have expected a first leaf on a sprout that thick to be showing more mature coloration. However, that is something else that may be different in our stronger ultraviolet, and lower humidity. Definitely worthwhile keeping an eye on that sprout, though, and any like it. A few months won't make much difference in cutting them off--a "takeover" usually needs a couple of years of neglect to accomplish!