LEAF COLOUR CHANGES IN CRASSULA (JADES)
What you see is the movement of a coloured water-soluble pigment called ANTHOCYANIN.
Crassula Sienna Sport showing great anthocyanin expression above:
In plants, anthocyanins plays a role not only in reproduction, but also in protection against various abiotic (environmental factors like drought, high salinity, temperature, cold or hot) and biotec stress (pathogen).
WHAT DOES ALL THIS MEAN WITH CRASSULA (JADE)?
Simple, a natural method of protection, a screen against stress with the plant, a genetic trait provided by nature for the plant, transient, accumulates and disappears when beneficial to the plant.
Not all Crassulas (Jades) have the same amount of anthocyanin, or express it the same way.
Expression can be just leaf margins, leaf blushing or a range or combination of colour that is quite dramatic over the year.
VARIEGATION vs ANTHOCYANIN EXPRESSION
Leaf variegation is seen in many ornamental plants including Crassula Ovata (Jades).
Variegation is a genetic trait, although variegation can be caused by virus.
Anthocyanin is a separate genetic trait altogether and quite different to variegation as anthocyanin can come and go within the leaves where variegation should be stable year round.