Can anyone tell me what this is?
Small shrub in pot
Euonymus fortunei also has a lot of varieties.
Both E. japonicus and E. fortunei can have color variations, and different leaf shape, though the scalloped edges is a pretty good ID feature.
As suggested by growin, El Dorado is a very good possibility- the new growth yellow and mature growth green is a good clue.
Thanks, I have now been able to discover that it is Euonymus japonicus 'Microphyllus Gold Dust'
E. microphyllus group has much smaller leaves than most of the other Euonymus. Leaf size would have been a good piece of information to help ID it.