Washingtonia petiole color metamorphosis?

[MSX]

Hello palmtalkers! I bought this young washingtonia a couple of weeks ago, since I wanted a cold hardy W.  fillifera I carefully selected the one that had all pure green petioles keeping in mind that this is one of the most distinctive features between filifera and robusta/filibusta, and the one that actually looked as a young healthy filifera baby palm. Here it is in its nursery pot.

I eventually planted it in the ground 5 days ago on March 25, it was all green and still looked as filifera then.

Today in the morning I decided  to water my young plant and to check out how it's settling in a new place, and I found out that all parts of the plant that were recently pure green have now become reddish-brown!  For a new place it's doing well - the palm gained about an inch of new growth in less than a week under full sun but I'm totally confused now how to choose my next Washingtonias knowing now that it can change the color scheme anytime! Have you guys had a similar experience when your previously believed filiferas suddenly turn into robustas/dominant filibustas? Such metamorphosis is a normal thing for Washies?  

Edited March 30, 2021 by MSX