Cause of purple petiole base

[Dimovi]

I have noticed that some of my Mediterranean fan palms and my Pindos have purple leaf sheaths and lower end of the petioles. Also my single Mule has that.

Are these different varieties or is this caused by some nutrient/environmental anomaly?

Otherwise the plants look healthy.

[Jim in Los Altos]

Just variations in those plants. It’s common to see in those species. They look very healthy. 

[sonoranfans]

This just shows a high anthocyanin content on the purple one.  A small amount of anthocyanin can change color.  Seedling plants respond to insect attack with an increase in anthocyanin.  The function of anthocyanin in plants is not entirely understood, it repels some insects, it attenuates sun from photosynthesis that might be overheating a plant.  My 4 small dictyosperma album rubrum seedlings showed intense red(anthocyanin color depends on plant sap pH) anthocyanin color where scale had damaged leaves before I removed it.  Plants that were not attacked or had minimal scale showed minimal color change.  Now about 3 months later, most of the red is gone, there have been no further scale issues.  Some papers stated a hypothesis that plants with more insect responsive production of anthocyanin have a lower risk of being ravaged by insects.  You might mark that one and take observations to see how it and its sib differ in the future growth.