I have some Ludwigia sp Red now. Under low light, it was still red, but more of an orangeish red. Now under my Ray 2, it's growing in dark blood red. I have some Ludwigia Rubin coming in today or tomorrow via the mail.
I was also curious about this, that I why I wanted some Rubin. If there is still interest, I'll post some pics in a few weeks after the Rubin settles in. I'll be mad if they are the same LOL! The guy I'm getting them from told me that the Rubin gets a much deeper red than the sp Red gets. Marketing??