royal farlowella

I currently own two catfish sold to me as "Farlowella whiptail". However, after doing some research online, this name can be associated with both sturisomatichthys panamense and aureus. They also both look rather similar, so for future breeding information could I have some help in IDing these...

I'm currently keeping 2 royal farlowella which are 2.5 and 3 inches respectively. A curious thing I notice is that the 3 inch one tends to have strange colour switches in which it gets really pale and loses all colour in the pattern, and then sometimes it regains the pattern and looks completely...