Is this a juvenal color???

[Magnum Man]

Prochilodus lineatus
I saw these listed on several of the monster fish sites, so I know they get huge... but in looking on line, I don't find any pictures that look like this...

Red Fin Prochilodus (Flagtail) – Vibrant Freshwater Fish for Aquariums

Shop Red Fin Prochilodus (Flagtail) – a peaceful, colorful freshwater fish perfect for community tanks. Learn about care, tank size, diet & compatibility.

robsaquatics.com

described at adult 12-14 inches here, I thought one may make an interesting tank mate with the silver dollars in my up coming 250 gallon...

most pictures look drab grey...

 

[Magnum Man]

coincidentally this seller ( whom I've never used before ) just got in a shipment of Elephant Nose's

 

[FranciscoB]

No, that is not juvenile color. Flagtail prochis ((Semaprochilodus) do not loose color with age.
The second picture is not a Semaprochilodus, but another Curimatid (close relative), sush as Prochilodus or Curimata.