The Stuart Strathearn "Dark Crystal" coloured pieces don't contain swirls. You'll find red and black, you might be very lucky and find blue and black.
Green and black, I've only ever seen in catalogue photos.
I suppose they did sort of carry on with similar designs - but they introduced moulds at Strathearn.
Very early on, at Monart, the working conditions and materials available were very primitive indeed, but they did have the expertise of Salvador and his sons were really rather talented too.
They could work miracles.
At Vasart, the wars got in the way of them being able to source brightly coloured enamels, which is why they're mostly all pale pastels. They were able to get hold of celadon glass, (that ubiqitous opaque pale green. You know the one.) frequently used in bathrooms and kitchens at the time.
Strathearn built on what went on in both; Stuart Strathearn was smaller and later and the Dark Crystal range is, i think, all they did in coloured glass.
They did do tall, slim, clear solifleurs, and a lot of small clear posy vases with engraving/etching, more a modern Stuart influence rather than the coloured one of the Ysarts.