two bundled Prunus blireiana samples using leaves from the same bunch, cooked in the same pot in the same bath without adjunct mordants...but on different silks.
the uppermost sample is on a piece of (unwashed) old Japanes silk, the lower on an (unwashed/unscoured) fragment of new Chinese silk.
there are a number of possible theories as to the colour difference, inlcuding : different species of mulberry leaves used to feed the silkmoths (which might also be different species), different soils and water used to nourish the plants, climate...etc
or something as simple as the water used to unravel the silk from the cocoon...the Chinese are known to use some alkalli in the scour...perhaps the Japanese manufacturer didn't.
who knows, but such magic is what makes dyeing with plants so satisfying.