With oscars, any cichlid for that matter,........ just because it looks one way, in a certain location, doesn't mean it will look that way in another location just a few miles away.
The left shot is a Chuco intermedia from 1 river in Mexico, the right pic is the same sprcies from another river only 15 miles away.
Topagraphy, vegetation, and light penetration (turbidity) all play a part in outward characteristics of what allows certin indiviuals to survive and favor certain color varants.
The Andinoacara variant below is found in vegetated area of Lake Gatun,
Below is a typical individual, found in rivers in the east, where aquatic vegetation is seldom found.
Above, collecting aquatic plants, in Lake Gatun.
Below a small stretch of the Mamoni river,